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Merge branches 'for-4.12/upstream' and 'for-4.12/klp-hybrid-consistency-model' into for-linus

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This commit is contained in:
Jiri Kosina
2017-05-01 21:49:28 +02:00
parent 77f8f39a2e e679af627f
commit a0841609f6
30 changed files with 1537 additions and 351 deletions
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Documentation/ABI/testing/sysfs-kernel-livepatch
+8
View File
@@ -25,6 +25,14 @@ Description:
code is currently applied. Writing 0 will disable the patch
while writing 1 will re-enable the patch.
What: /sys/kernel/livepatch/<patch>/transition
Date: Feb 2017
KernelVersion: 4.12.0
Contact: live-patching@vger.kernel.org
Description:
An attribute which indicates whether the patch is currently in
transition.
What: /sys/kernel/livepatch/<patch>/<object>
Date: Nov 2014
KernelVersion: 3.19.0
Documentation/filesystems/proc.txt
+18
View File
@@ -44,6 +44,7 @@ Table of Contents
3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
3.9 /proc/<pid>/map_files - Information about memory mapped files
3.10 /proc/<pid>/timerslack_ns - Task timerslack value
3.11 /proc/<pid>/patch_state - Livepatch patch operation state
4 Configuring procfs
4.1 Mount options
@@ -1887,6 +1888,23 @@ Valid values are from 0 - ULLONG_MAX
An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
permissions on the task specified to change its timerslack_ns value.
3.11 /proc/<pid>/patch_state - Livepatch patch operation state
-----------------------------------------------------------------
When CONFIG_LIVEPATCH is enabled, this file displays the value of the
patch state for the task.
A value of '-1' indicates that no patch is in transition.
A value of '0' indicates that a patch is in transition and the task is
unpatched. If the patch is being enabled, then the task hasn't been
patched yet. If the patch is being disabled, then the task has already
been unpatched.
A value of '1' indicates that a patch is in transition and the task is
patched. If the patch is being enabled, then the task has already been
patched. If the patch is being disabled, then the task hasn't been
unpatched yet.
------------------------------------------------------------------------------
Configuring procfs
Documentation/livepatch/livepatch.txt
+169 -39
View File
@@ -72,7 +72,8 @@ example, they add a NULL pointer or a boundary check, fix a race by adding
a missing memory barrier, or add some locking around a critical section.
Most of these changes are self contained and the function presents itself
the same way to the rest of the system. In this case, the functions might
be updated independently one by one.
be updated independently one by one. (This can be done by setting the
'immediate' flag in the klp_patch struct.)
But there are more complex fixes. For example, a patch might change
ordering of locking in multiple functions at the same time. Or a patch
@@ -86,20 +87,141 @@ or no data are stored in the modified structures at the moment.
The theory about how to apply functions a safe way is rather complex.
The aim is to define a so-called consistency model. It attempts to define
conditions when the new implementation could be used so that the system
stays consistent. The theory is not yet finished. See the discussion at
https://lkml.kernel.org/r/20141107140458.GA21774@suse.cz
stays consistent.
The current consistency model is very simple. It guarantees that either
the old or the new function is called. But various functions get redirected
one by one without any synchronization.
Livepatch has a consistency model which is a hybrid of kGraft and
kpatch: it uses kGraft's per-task consistency and syscall barrier
switching combined with kpatch's stack trace switching. There are also
a number of fallback options which make it quite flexible.
In other words, the current implementation _never_ modifies the behavior
in the middle of the call. It is because it does _not_ rewrite the entire
function in the memory. Instead, the function gets redirected at the
very beginning. But this redirection is used immediately even when
some other functions from the same patch have not been redirected yet.
Patches are applied on a per-task basis, when the task is deemed safe to
switch over. When a patch is enabled, livepatch enters into a
transition state where tasks are converging to the patched state.
Usually this transition state can complete in a few seconds. The same
sequence occurs when a patch is disabled, except the tasks converge from
the patched state to the unpatched state.
See also the section "Limitations" below.
An interrupt handler inherits the patched state of the task it
interrupts. The same is true for forked tasks: the child inherits the
patched state of the parent.
Livepatch uses several complementary approaches to determine when it's
safe to patch tasks:
1. The first and most effective approach is stack checking of sleeping
tasks. If no affected functions are on the stack of a given task,
the task is patched. In most cases this will patch most or all of
the tasks on the first try. Otherwise it'll keep trying
periodically. This option is only available if the architecture has
reliable stacks (HAVE_RELIABLE_STACKTRACE).
2. The second approach, if needed, is kernel exit switching. A
task is switched when it returns to user space from a system call, a
user space IRQ, or a signal. It's useful in the following cases:
a) Patching I/O-bound user tasks which are sleeping on an affected
function. In this case you have to send SIGSTOP and SIGCONT to
force it to exit the kernel and be patched.
b) Patching CPU-bound user tasks. If the task is highly CPU-bound
then it will get patched the next time it gets interrupted by an
IRQ.
c) In the future it could be useful for applying patches for
architectures which don't yet have HAVE_RELIABLE_STACKTRACE. In
this case you would have to signal most of the tasks on the
system. However this isn't supported yet because there's
currently no way to patch kthreads without
HAVE_RELIABLE_STACKTRACE.
3. For idle "swapper" tasks, since they don't ever exit the kernel, they
instead have a klp_update_patch_state() call in the idle loop which
allows them to be patched before the CPU enters the idle state.
(Note there's not yet such an approach for kthreads.)
All the above approaches may be skipped by setting the 'immediate' flag
in the 'klp_patch' struct, which will disable per-task consistency and
patch all tasks immediately. This can be useful if the patch doesn't
change any function or data semantics. Note that, even with this flag
set, it's possible that some tasks may still be running with an old
version of the function, until that function returns.
There's also an 'immediate' flag in the 'klp_func' struct which allows
you to specify that certain functions in the patch can be applied
without per-task consistency. This might be useful if you want to patch
a common function like schedule(), and the function change doesn't need
consistency but the rest of the patch does.
For architectures which don't have HAVE_RELIABLE_STACKTRACE, the user
must set patch->immediate which causes all tasks to be patched
immediately. This option should be used with care, only when the patch
doesn't change any function or data semantics.
In the future, architectures which don't have HAVE_RELIABLE_STACKTRACE
may be allowed to use per-task consistency if we can come up with
another way to patch kthreads.
The /sys/kernel/livepatch/<patch>/transition file shows whether a patch
is in transition. Only a single patch (the topmost patch on the stack)
can be in transition at a given time. A patch can remain in transition
indefinitely, if any of the tasks are stuck in the initial patch state.
A transition can be reversed and effectively canceled by writing the
opposite value to the /sys/kernel/livepatch/<patch>/enabled file while
the transition is in progress. Then all the tasks will attempt to
converge back to the original patch state.
There's also a /proc/<pid>/patch_state file which can be used to
determine which tasks are blocking completion of a patching operation.
If a patch is in transition, this file shows 0 to indicate the task is
unpatched and 1 to indicate it's patched. Otherwise, if no patch is in
transition, it shows -1. Any tasks which are blocking the transition
can be signaled with SIGSTOP and SIGCONT to force them to change their
patched state.
3.1 Adding consistency model support to new architectures
---------------------------------------------------------
For adding consistency model support to new architectures, there are a
few options:
1) Add CONFIG_HAVE_RELIABLE_STACKTRACE. This means porting objtool, and
for non-DWARF unwinders, also making sure there's a way for the stack
tracing code to detect interrupts on the stack.
2) Alternatively, ensure that every kthread has a call to
klp_update_patch_state() in a safe location. Kthreads are typically
in an infinite loop which does some action repeatedly. The safe
location to switch the kthread's patch state would be at a designated
point in the loop where there are no locks taken and all data
structures are in a well-defined state.
The location is clear when using workqueues or the kthread worker
API. These kthreads process independent actions in a generic loop.
It's much more complicated with kthreads which have a custom loop.
There the safe location must be carefully selected on a case-by-case
basis.
In that case, arches without HAVE_RELIABLE_STACKTRACE would still be
able to use the non-stack-checking parts of the consistency model:
a) patching user tasks when they cross the kernel/user space
boundary; and
b) patching kthreads and idle tasks at their designated patch points.
This option isn't as good as option 1 because it requires signaling
user tasks and waking kthreads to patch them. But it could still be
a good backup option for those architectures which don't have
reliable stack traces yet.
In the meantime, patches for such architectures can bypass the
consistency model by setting klp_patch.immediate to true. This option
is perfectly fine for patches which don't change the semantics of the
patched functions. In practice, this is usable for ~90% of security
fixes. Use of this option also means the patch can't be unloaded after
it has been disabled.
4. Livepatch module
@@ -134,7 +256,7 @@ Documentation/livepatch/module-elf-format.txt for more details.
4.2. Metadata
------------
-------------
The patch is described by several structures that split the information
into three levels:
@@ -156,6 +278,9 @@ into three levels:
only for a particular object ( vmlinux or a kernel module ). Note that
kallsyms allows for searching symbols according to the object name.
There's also an 'immediate' flag which, when set, patches the
function immediately, bypassing the consistency model safety checks.
+ struct klp_object defines an array of patched functions (struct
klp_func) in the same object. Where the object is either vmlinux
(NULL) or a module name.
@@ -172,10 +297,13 @@ into three levels:
This structure handles all patched functions consistently and eventually,
synchronously. The whole patch is applied only when all patched
symbols are found. The only exception are symbols from objects
(kernel modules) that have not been loaded yet. Also if a more complex
consistency model is supported then a selected unit (thread,
kernel as a whole) will see the new code from the entire patch
only when it is in a safe state.
(kernel modules) that have not been loaded yet.
Setting the 'immediate' flag applies the patch to all tasks
immediately, bypassing the consistency model safety checks.
For more details on how the patch is applied on a per-task basis,
see the "Consistency model" section.
4.3. Livepatch module handling
@@ -188,8 +316,15 @@ section "Livepatch life-cycle" below for more details about these
two operations.
Module removal is only safe when there are no users of the underlying
functions. The immediate consistency model is not able to detect this;
therefore livepatch modules cannot be removed. See "Limitations" below.
functions. The immediate consistency model is not able to detect this. The
code just redirects the functions at the very beginning and it does not
check if the functions are in use. In other words, it knows when the
functions get called but it does not know when the functions return.
Therefore it cannot be decided when the livepatch module can be safely
removed. This is solved by a hybrid consistency model. When the system is
transitioned to a new patch state (patched/unpatched) it is guaranteed that
no task sleeps or runs in the old code.
5. Livepatch life-cycle
=======================
@@ -239,9 +374,15 @@ Registered patches might be enabled either by calling klp_enable_patch() or
by writing '1' to /sys/kernel/livepatch/<name>/enabled. The system will
start using the new implementation of the patched functions at this stage.
In particular, if an original function is patched for the first time, a
function specific struct klp_ops is created and an universal ftrace handler
is registered.
When a patch is enabled, livepatch enters into a transition state where
tasks are converging to the patched state. This is indicated by a value
of '1' in /sys/kernel/livepatch/<name>/transition. Once all tasks have
been patched, the 'transition' value changes to '0'. For more
information about this process, see the "Consistency model" section.
If an original function is patched for the first time, a function
specific struct klp_ops is created and an universal ftrace handler is
registered.
Functions might be patched multiple times. The ftrace handler is registered
only once for the given function. Further patches just add an entry to the
@@ -261,6 +402,12 @@ by writing '0' to /sys/kernel/livepatch/<name>/enabled. At this stage
either the code from the previously enabled patch or even the original
code gets used.
When a patch is disabled, livepatch enters into a transition state where
tasks are converging to the unpatched state. This is indicated by a
value of '1' in /sys/kernel/livepatch/<name>/transition. Once all tasks
have been unpatched, the 'transition' value changes to '0'. For more
information about this process, see the "Consistency model" section.
Here all the functions (struct klp_func) associated with the to-be-disabled
patch are removed from the corresponding struct klp_ops. The ftrace handler
is unregistered and the struct klp_ops is freed when the func_stack list
@@ -329,23 +476,6 @@ The current Livepatch implementation has several limitations:
by "notrace".
+ Livepatch modules can not be removed.
The current implementation just redirects the functions at the very
beginning. It does not check if the functions are in use. In other
words, it knows when the functions get called but it does not
know when the functions return. Therefore it can not decide when
the livepatch module can be safely removed.
This will get most likely solved once a more complex consistency model
is supported. The idea is that a safe state for patching should also
mean a safe state for removing the patch.
Note that the patch itself might get disabled by writing zero
to /sys/kernel/livepatch/<patch>/enabled. It causes that the new
code will not longer get called. But it does not guarantee
that anyone is not sleeping anywhere in the new code.
+ Livepatch works reliably only when the dynamic ftrace is located at
the very beginning of the function.
arch/Kconfig
+6
View File
@@ -713,6 +713,12 @@ config HAVE_STACK_VALIDATION
Architecture supports the 'objtool check' host tool command, which
performs compile-time stack metadata validation.
config HAVE_RELIABLE_STACKTRACE
bool
help
Architecture has a save_stack_trace_tsk_reliable() function which
only returns a stack trace if it can guarantee the trace is reliable.
config HAVE_ARCH_HASH
bool
default n
arch/powerpc/include/asm/thread_info.h
+3 -1
View File
@@ -92,6 +92,7 @@ static inline struct thread_info *current_thread_info(void)
TIF_NEED_RESCHED */
#define TIF_32BIT 4 /* 32 bit binary */
#define TIF_RESTORE_TM 5 /* need to restore TM FP/VEC/VSX */
#define TIF_PATCH_PENDING 6 /* pending live patching update */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
#define TIF_SINGLESTEP 8 /* singlestepping active */
#define TIF_NOHZ 9 /* in adaptive nohz mode */
@@ -115,6 +116,7 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_32BIT (1<<TIF_32BIT)
#define _TIF_RESTORE_TM (1<<TIF_RESTORE_TM)
#define _TIF_PATCH_PENDING (1<<TIF_PATCH_PENDING)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
@@ -131,7 +133,7 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_USER_WORK_MASK (_TIF_SIGPENDING | _TIF_NEED_RESCHED | \
_TIF_NOTIFY_RESUME | _TIF_UPROBE | \
_TIF_RESTORE_TM)
_TIF_RESTORE_TM | _TIF_PATCH_PENDING)
#define _TIF_PERSYSCALL_MASK (_TIF_RESTOREALL|_TIF_NOERROR)
/* Bits in local_flags */
arch/powerpc/kernel/signal.c
+4
View File
@@ -14,6 +14,7 @@
#include <linux/uprobes.h>
#include <linux/key.h>
#include <linux/context_tracking.h>
#include <linux/livepatch.h>
#include <asm/hw_breakpoint.h>
#include <linux/uaccess.h>
#include <asm/unistd.h>
@@ -162,6 +163,9 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
tracehook_notify_resume(regs);
}
if (thread_info_flags & _TIF_PATCH_PENDING)
klp_update_patch_state(current);
user_enter();
}
arch/s390/include/asm/thread_info.h
+16 -8
View File
@@ -51,14 +51,13 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
/*
* thread information flags bit numbers
*/
/* _TIF_WORK bits */
#define TIF_NOTIFY_RESUME 0 /* callback before returning to user */
#define TIF_SIGPENDING 1 /* signal pending */
#define TIF_NEED_RESCHED 2 /* rescheduling necessary */
#define TIF_SYSCALL_TRACE 3 /* syscall trace active */
#define TIF_SYSCALL_AUDIT 4 /* syscall auditing active */
#define TIF_SECCOMP 5 /* secure computing */
#define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */
#define TIF_UPROBE 7 /* breakpointed or single-stepping */
#define TIF_UPROBE 3 /* breakpointed or single-stepping */
#define TIF_PATCH_PENDING 4 /* pending live patching update */
#define TIF_31BIT 16 /* 32bit process */
#define TIF_MEMDIE 17 /* is terminating due to OOM killer */
#define TIF_RESTORE_SIGMASK 18 /* restore signal mask in do_signal() */
@@ -66,15 +65,24 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
#define TIF_BLOCK_STEP 20 /* This task is block stepped */
#define TIF_UPROBE_SINGLESTEP 21 /* This task is uprobe single stepped */
/* _TIF_TRACE bits */
#define TIF_SYSCALL_TRACE 24 /* syscall trace active */
#define TIF_SYSCALL_AUDIT 25 /* syscall auditing active */
#define TIF_SECCOMP 26 /* secure computing */
#define TIF_SYSCALL_TRACEPOINT 27 /* syscall tracepoint instrumentation */
#define _TIF_NOTIFY_RESUME _BITUL(TIF_NOTIFY_RESUME)
#define _TIF_SIGPENDING _BITUL(TIF_SIGPENDING)
#define _TIF_NEED_RESCHED _BITUL(TIF_NEED_RESCHED)
#define _TIF_UPROBE _BITUL(TIF_UPROBE)
#define _TIF_PATCH_PENDING _BITUL(TIF_PATCH_PENDING)
#define _TIF_31BIT _BITUL(TIF_31BIT)
#define _TIF_SINGLE_STEP _BITUL(TIF_SINGLE_STEP)
#define _TIF_SYSCALL_TRACE _BITUL(TIF_SYSCALL_TRACE)
#define _TIF_SYSCALL_AUDIT _BITUL(TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP _BITUL(TIF_SECCOMP)
#define _TIF_SYSCALL_TRACEPOINT _BITUL(TIF_SYSCALL_TRACEPOINT)
#define _TIF_UPROBE _BITUL(TIF_UPROBE)
#define _TIF_31BIT _BITUL(TIF_31BIT)
#define _TIF_SINGLE_STEP _BITUL(TIF_SINGLE_STEP)
#endif /* _ASM_THREAD_INFO_H */
arch/s390/kernel/entry.S
+30 -1
View File
@@ -47,7 +47,7 @@ STACK_SIZE = 1 << STACK_SHIFT
STACK_INIT = STACK_SIZE - STACK_FRAME_OVERHEAD - __PT_SIZE
_TIF_WORK = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
_TIF_UPROBE)
_TIF_UPROBE | _TIF_PATCH_PENDING)
_TIF_TRACE = (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \
_TIF_SYSCALL_TRACEPOINT)
_CIF_WORK = (_CIF_MCCK_PENDING | _CIF_ASCE_PRIMARY | \
@@ -334,6 +334,11 @@ ENTRY(system_call)
#endif
TSTMSK __PT_FLAGS(%r11),_PIF_PER_TRAP
jo .Lsysc_singlestep
#ifdef CONFIG_LIVEPATCH
TSTMSK __TI_flags(%r12),_TIF_PATCH_PENDING
jo .Lsysc_patch_pending # handle live patching just before
# signals and possible syscall restart
#endif
TSTMSK __TI_flags(%r12),_TIF_SIGPENDING
jo .Lsysc_sigpending
TSTMSK __TI_flags(%r12),_TIF_NOTIFY_RESUME
@@ -408,6 +413,16 @@ ENTRY(system_call)
jg uprobe_notify_resume
#endif
#
# _TIF_PATCH_PENDING is set, call klp_update_patch_state
#
#ifdef CONFIG_LIVEPATCH
.Lsysc_patch_pending:
lg %r2,__LC_CURRENT # pass pointer to task struct
larl %r14,.Lsysc_return
jg klp_update_patch_state
#endif
#
# _PIF_PER_TRAP is set, call do_per_trap
#
@@ -659,6 +674,10 @@ ENTRY(io_int_handler)
jo .Lio_mcck_pending
TSTMSK __TI_flags(%r12),_TIF_NEED_RESCHED
jo .Lio_reschedule
#ifdef CONFIG_LIVEPATCH
TSTMSK __TI_flags(%r12),_TIF_PATCH_PENDING
jo .Lio_patch_pending
#endif
TSTMSK __TI_flags(%r12),_TIF_SIGPENDING
jo .Lio_sigpending
TSTMSK __TI_flags(%r12),_TIF_NOTIFY_RESUME
@@ -707,6 +726,16 @@ ENTRY(io_int_handler)
TRACE_IRQS_OFF
j .Lio_return
#
# _TIF_PATCH_PENDING is set, call klp_update_patch_state
#
#ifdef CONFIG_LIVEPATCH
.Lio_patch_pending:
lg %r2,__LC_CURRENT # pass pointer to task struct
larl %r14,.Lio_return
jg klp_update_patch_state
#endif
#
# _TIF_SIGPENDING or is set, call do_signal
#
arch/x86/Kconfig
+1
View File
@@ -160,6 +160,7 @@ config X86
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_RELIABLE_STACKTRACE if X86_64 && FRAME_POINTER && STACK_VALIDATION
select HAVE_STACK_VALIDATION if X86_64
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_UNSTABLE_SCHED_CLOCK
arch/x86/entry/common.c
+6 -3
View File
@@ -22,6 +22,7 @@
#include <linux/context_tracking.h>
#include <linux/user-return-notifier.h>
#include <linux/uprobes.h>
#include <linux/livepatch.h>
#include <asm/desc.h>
#include <asm/traps.h>
@@ -130,14 +131,13 @@ static long syscall_trace_enter(struct pt_regs *regs)
#define EXIT_TO_USERMODE_LOOP_FLAGS \
(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
_TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY)
_TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY | _TIF_PATCH_PENDING)
static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
{
/*
* In order to return to user mode, we need to have IRQs off with
* none of _TIF_SIGPENDING, _TIF_NOTIFY_RESUME, _TIF_USER_RETURN_NOTIFY,
* _TIF_UPROBE, or _TIF_NEED_RESCHED set. Several of these flags
* none of EXIT_TO_USERMODE_LOOP_FLAGS set. Several of these flags
* can be set at any time on preemptable kernels if we have IRQs on,
* so we need to loop. Disabling preemption wouldn't help: doing the
* work to clear some of the flags can sleep.
@@ -164,6 +164,9 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
if (cached_flags & _TIF_USER_RETURN_NOTIFY)
fire_user_return_notifiers();
if (cached_flags & _TIF_PATCH_PENDING)
klp_update_patch_state(current);
/* Disable IRQs and retry */
local_irq_disable();
arch/x86/include/asm/thread_info.h
+7 -6
View File
@@ -73,9 +73,6 @@ struct thread_info {
* thread information flags
* - these are process state flags that various assembly files
* may need to access
* - pending work-to-be-done flags are in LSW
* - other flags in MSW
* Warning: layout of LSW is hardcoded in entry.S
*/
#define TIF_SYSCALL_TRACE 0 /* syscall trace active */
#define TIF_NOTIFY_RESUME 1 /* callback before returning to user */
@@ -87,6 +84,7 @@ struct thread_info {
#define TIF_SECCOMP 8 /* secure computing */
#define TIF_USER_RETURN_NOTIFY 11 /* notify kernel of userspace return */
#define TIF_UPROBE 12 /* breakpointed or singlestepping */
#define TIF_PATCH_PENDING 13 /* pending live patching update */
#define TIF_NOTSC 16 /* TSC is not accessible in userland */
#define TIF_IA32 17 /* IA32 compatibility process */
#define TIF_NOHZ 19 /* in adaptive nohz mode */
@@ -103,13 +101,14 @@ struct thread_info {
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_SINGLESTEP (1 << TIF_SINGLESTEP)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_SINGLESTEP (1 << TIF_SINGLESTEP)
#define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
#define _TIF_USER_RETURN_NOTIFY (1 << TIF_USER_RETURN_NOTIFY)
#define _TIF_UPROBE (1 << TIF_UPROBE)
#define _TIF_PATCH_PENDING (1 << TIF_PATCH_PENDING)
#define _TIF_NOTSC (1 << TIF_NOTSC)
#define _TIF_IA32 (1 << TIF_IA32)
#define _TIF_NOHZ (1 << TIF_NOHZ)
@@ -133,8 +132,10 @@ struct thread_info {
/* work to do on any return to user space */
#define _TIF_ALLWORK_MASK \
((0x0000FFFF & ~_TIF_SECCOMP) | _TIF_SYSCALL_TRACEPOINT | \
_TIF_NOHZ)
(_TIF_SYSCALL_TRACE | _TIF_NOTIFY_RESUME | _TIF_SIGPENDING | \
_TIF_NEED_RESCHED | _TIF_SINGLESTEP | _TIF_SYSCALL_EMU | \
_TIF_SYSCALL_AUDIT | _TIF_USER_RETURN_NOTIFY | _TIF_UPROBE | \
_TIF_PATCH_PENDING | _TIF_NOHZ | _TIF_SYSCALL_TRACEPOINT)
/* flags to check in __switch_to() */
#define _TIF_WORK_CTXSW \
arch/x86/include/asm/unwind.h
+6
View File
@@ -11,6 +11,7 @@ struct unwind_state {
unsigned long stack_mask;
struct task_struct *task;
int graph_idx;
bool error;
#ifdef CONFIG_FRAME_POINTER
unsigned long *bp, *orig_sp;
struct pt_regs *regs;
@@ -40,6 +41,11 @@ void unwind_start(struct unwind_state *state, struct task_struct *task,
__unwind_start(state, task, regs, first_frame);
}
static inline bool unwind_error(struct unwind_state *state)
{
return state->error;
}
#ifdef CONFIG_FRAME_POINTER
static inline
arch/x86/kernel/stacktrace.c
+95 -1
View File
@@ -76,6 +76,101 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
}
EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
#define STACKTRACE_DUMP_ONCE(task) ({ \
static bool __section(.data.unlikely) __dumped; \
\
if (!__dumped) { \
__dumped = true; \
WARN_ON(1); \
show_stack(task, NULL); \
} \
})
static int __save_stack_trace_reliable(struct stack_trace *trace,
struct task_struct *task)
{
struct unwind_state state;
struct pt_regs *regs;
unsigned long addr;
for (unwind_start(&state, task, NULL, NULL); !unwind_done(&state);
unwind_next_frame(&state)) {
regs = unwind_get_entry_regs(&state);
if (regs) {
/*
* Kernel mode registers on the stack indicate an
* in-kernel interrupt or exception (e.g., preemption
* or a page fault), which can make frame pointers
* unreliable.
*/
if (!user_mode(regs))
return -EINVAL;
/*
* The last frame contains the user mode syscall
* pt_regs. Skip it and finish the unwind.
*/
unwind_next_frame(&state);
if (!unwind_done(&state)) {
STACKTRACE_DUMP_ONCE(task);
return -EINVAL;
}
break;
}
addr = unwind_get_return_address(&state);
/*
* A NULL or invalid return address probably means there's some
* generated code which __kernel_text_address() doesn't know
* about.
*/
if (!addr) {
STACKTRACE_DUMP_ONCE(task);
return -EINVAL;
}
if (save_stack_address(trace, addr, false))
return -EINVAL;
}
/* Check for stack corruption */
if (unwind_error(&state)) {
STACKTRACE_DUMP_ONCE(task);
return -EINVAL;
}
if (trace->nr_entries < trace->max_entries)
trace->entries[trace->nr_entries++] = ULONG_MAX;
return 0;
}
/*
* This function returns an error if it detects any unreliable features of the
* stack. Otherwise it guarantees that the stack trace is reliable.
*
* If the task is not 'current', the caller *must* ensure the task is inactive.
*/
int save_stack_trace_tsk_reliable(struct task_struct *tsk,
struct stack_trace *trace)
{
int ret;
if (!try_get_task_stack(tsk))
return -EINVAL;
ret = __save_stack_trace_reliable(trace, tsk);
put_task_stack(tsk);
return ret;
}
#endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */
/* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */
struct stack_frame_user {
@@ -138,4 +233,3 @@ void save_stack_trace_user(struct stack_trace *trace)
if (trace->nr_entries < trace->max_entries)
trace->entries[trace->nr_entries++] = ULONG_MAX;
}
arch/x86/kernel/unwind_frame.c
+2
View File
@@ -225,6 +225,8 @@ bool unwind_next_frame(struct unwind_state *state)
return true;
bad_address:
state->error = true;
/*
* When unwinding a non-current task, the task might actually be
* running on another CPU, in which case it could be modifying its
fs/proc/base.c
+15
View File
@@ -2834,6 +2834,15 @@ static int proc_pid_personality(struct seq_file *m, struct pid_namespace *ns,
return err;
}
#ifdef CONFIG_LIVEPATCH
static int proc_pid_patch_state(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
seq_printf(m, "%d\n", task->patch_state);
return 0;
}
#endif /* CONFIG_LIVEPATCH */
/*
* Thread groups
*/
@@ -2933,6 +2942,9 @@ static const struct pid_entry tgid_base_stuff[] = {
REG("timers", S_IRUGO, proc_timers_operations),
#endif
REG("timerslack_ns", S_IRUGO|S_IWUGO, proc_pid_set_timerslack_ns_operations),
#ifdef CONFIG_LIVEPATCH
ONE("patch_state", S_IRUSR, proc_pid_patch_state),
#endif
};
static int proc_tgid_base_readdir(struct file *file, struct dir_context *ctx)
@@ -3315,6 +3327,9 @@ static const struct pid_entry tid_base_stuff[] = {
REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
REG("setgroups", S_IRUGO|S_IWUSR, proc_setgroups_operations),
#endif
#ifdef CONFIG_LIVEPATCH
ONE("patch_state", S_IRUSR, proc_pid_patch_state),
#endif
};
static int proc_tid_base_readdir(struct file *file, struct dir_context *ctx)
include/linux/init_task.h
+9
View File
@@ -15,6 +15,7 @@
#include <linux/sched/autogroup.h>
#include <net/net_namespace.h>
#include <linux/sched/rt.h>
#include <linux/livepatch.h>
#include <linux/mm_types.h>
#include <asm/thread_info.h>
@@ -202,6 +203,13 @@ extern struct cred init_cred;
# define INIT_KASAN(tsk)
#endif
#ifdef CONFIG_LIVEPATCH
# define INIT_LIVEPATCH(tsk) \
.patch_state = KLP_UNDEFINED,
#else
# define INIT_LIVEPATCH(tsk)
#endif
#ifdef CONFIG_THREAD_INFO_IN_TASK
# define INIT_TASK_TI(tsk) \
.thread_info = INIT_THREAD_INFO(tsk), \
@@ -288,6 +296,7 @@ extern struct cred init_cred;
INIT_VTIME(tsk) \
INIT_NUMA_BALANCING(tsk) \
INIT_KASAN(tsk) \
INIT_LIVEPATCH(tsk) \
}
include/linux/livepatch.h
+56 -12
View File
@@ -23,15 +23,16 @@
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/completion.h>
#if IS_ENABLED(CONFIG_LIVEPATCH)
#include <asm/livepatch.h>
enum klp_state {
KLP_DISABLED,
KLP_ENABLED
};
/* task patch states */
#define KLP_UNDEFINED -1
#define KLP_UNPATCHED 0
#define KLP_PATCHED 1
/**
* struct klp_func - function structure for live patching
@@ -39,10 +40,29 @@ enum klp_state {
* @new_func: pointer to the patched function code
* @old_sympos: a hint indicating which symbol position the old function
* can be found (optional)
* @immediate: patch the func immediately, bypassing safety mechanisms
* @old_addr: the address of the function being patched
* @kobj: kobject for sysfs resources
* @state: tracks function-level patch application state
* @stack_node: list node for klp_ops func_stack list
* @old_size: size of the old function
* @new_size: size of the new function
* @patched: the func has been added to the klp_ops list
* @transition: the func is currently being applied or reverted
*
* The patched and transition variables define the func's patching state. When
* patching, a func is always in one of the following states:
*
* patched=0 transition=0: unpatched
* patched=0 transition=1: unpatched, temporary starting state
* patched=1 transition=1: patched, may be visible to some tasks
* patched=1 transition=0: patched, visible to all tasks
*
* And when unpatching, it goes in the reverse order:
*
* patched=1 transition=0: patched, visible to all tasks
* patched=1 transition=1: patched, may be visible to some tasks
* patched=0 transition=1: unpatched, temporary ending state
* patched=0 transition=0: unpatched
*/
struct klp_func {
/* external */
@@ -56,12 +76,15 @@ struct klp_func {
* in kallsyms for the given object is used.
*/
unsigned long old_sympos;
bool immediate;
/* internal */
unsigned long old_addr;
struct kobject kobj;
enum klp_state state;
struct list_head stack_node;
unsigned long old_size, new_size;
bool patched;
bool transition;
};
/**
@@ -70,8 +93,8 @@ struct klp_func {
* @funcs: function entries for functions to be patched in the object
* @kobj: kobject for sysfs resources
* @mod: kernel module associated with the patched object
* (NULL for vmlinux)
* @state: tracks object-level patch application state
* (NULL for vmlinux)
* @patched: the object's funcs have been added to the klp_ops list
*/
struct klp_object {
/* external */
@@ -81,26 +104,30 @@ struct klp_object {
/* internal */
struct kobject kobj;
struct module *mod;
enum klp_state state;
bool patched;
};
/**
* struct klp_patch - patch structure for live patching
* @mod: reference to the live patch module
* @objs: object entries for kernel objects to be patched
* @immediate: patch all funcs immediately, bypassing safety mechanisms
* @list: list node for global list of registered patches
* @kobj: kobject for sysfs resources
* @state: tracks patch-level application state
* @enabled: the patch is enabled (but operation may be incomplete)
* @finish: for waiting till it is safe to remove the patch module
*/
struct klp_patch {
/* external */
struct module *mod;
struct klp_object *objs;
bool immediate;
/* internal */
struct list_head list;
struct kobject kobj;
enum klp_state state;
bool enabled;
struct completion finish;
};
#define klp_for_each_object(patch, obj) \
@@ -123,10 +150,27 @@ void arch_klp_init_object_loaded(struct klp_patch *patch,
int klp_module_coming(struct module *mod);
void klp_module_going(struct module *mod);
void klp_copy_process(struct task_struct *child);
void klp_update_patch_state(struct task_struct *task);
static inline bool klp_patch_pending(struct task_struct *task)
{
return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
}
static inline bool klp_have_reliable_stack(void)
{
return IS_ENABLED(CONFIG_STACKTRACE) &&
IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
}
#else /* !CONFIG_LIVEPATCH */
static inline int klp_module_coming(struct module *mod) { return 0; }
static inline void klp_module_going(struct module *mod) { }
static inline void klp_module_going(struct module *mod) {}
static inline bool klp_patch_pending(struct task_struct *task) { return false; }
static inline void klp_update_patch_state(struct task_struct *task) {}
static inline void klp_copy_process(struct task_struct *child) {}
#endif /* CONFIG_LIVEPATCH */
include/linux/sched.h
+3
View File
@@ -1037,6 +1037,9 @@ struct task_struct {
#ifdef CONFIG_THREAD_INFO_IN_TASK
/* A live task holds one reference: */
atomic_t stack_refcount;
#endif
#ifdef CONFIG_LIVEPATCH
int patch_state;
#endif
/* CPU-specific state of this task: */
struct thread_struct thread;
include/linux/stacktrace.h
+6 -3
View File
@@ -18,6 +18,8 @@ extern void save_stack_trace_regs(struct pt_regs *regs,
struct stack_trace *trace);
extern void save_stack_trace_tsk(struct task_struct *tsk,
struct stack_trace *trace);
extern int save_stack_trace_tsk_reliable(struct task_struct *tsk,
struct stack_trace *trace);
extern void print_stack_trace(struct stack_trace *trace, int spaces);
extern int snprint_stack_trace(char *buf, size_t size,
@@ -29,12 +31,13 @@ extern void save_stack_trace_user(struct stack_trace *trace);
# define save_stack_trace_user(trace) do { } while (0)
#endif
#else
#else /* !CONFIG_STACKTRACE */
# define save_stack_trace(trace) do { } while (0)
# define save_stack_trace_tsk(tsk, trace) do { } while (0)
# define save_stack_trace_user(trace) do { } while (0)
# define print_stack_trace(trace, spaces) do { } while (0)
# define snprint_stack_trace(buf, size, trace, spaces) do { } while (0)
#endif
# define save_stack_trace_tsk_reliable(tsk, trace) ({ -ENOSYS; })
#endif /* CONFIG_STACKTRACE */
#endif
#endif /* __LINUX_STACKTRACE_H */
kernel/fork.c
+3
View File
@@ -87,6 +87,7 @@
#include <linux/compiler.h>
#include <linux/sysctl.h>
#include <linux/kcov.h>
#include <linux/livepatch.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -1797,6 +1798,8 @@ static __latent_entropy struct task_struct *copy_process(
p->parent_exec_id = current->self_exec_id;
}
klp_copy_process(p);
spin_lock(&current->sighand->siglock);
/*

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