Pull cgroup fix from Tejun Heo:
"Waiman's fix for a cgroup2 cpuset bug where it could miss nodes which
were hot-added"
* 'for-5.18-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup/cpuset: Remove cpus_allowed/mems_allowed setup in cpuset_init_smp()
Pull timer fix from Thomas Gleixner:
"A fix and an email address update:
- Mark the NMI safe time accessors notrace to prevent tracer
recursion when they are selected as trace clocks.
- John Stultz has a new email address"
* tag 'timers-urgent-2022-05-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timekeeping: Mark NMI safe time accessors as notrace
MAINTAINERS: Update email address for John Stultz
Pull irq fix from Thomas Gleixner:
"A fix for the threaded interrupt core.
A quick sequence of request/free_irq() can result in a hang because
the interrupt thread did not reach the thread function and got stopped
in the kthread core already. That leaves a state active counter
arround which makes a invocation of synchronized_irq() on that
interrupt hang forever.
Ensure that the thread reached the thread function in request_irq() to
prevent that"
* tag 'irq-urgent-2022-05-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
genirq: Synchronize interrupt thread startup
There are 3 places where the cpu and node masks of the top cpuset can
be initialized in the order they are executed:
1) start_kernel -> cpuset_init()
2) start_kernel -> cgroup_init() -> cpuset_bind()
3) kernel_init_freeable() -> do_basic_setup() -> cpuset_init_smp()
The first cpuset_init() call just sets all the bits in the masks.
The second cpuset_bind() call sets cpus_allowed and mems_allowed to the
default v2 values. The third cpuset_init_smp() call sets them back to
v1 values.
For systems with cgroup v2 setup, cpuset_bind() is called once. As a
result, cpu and memory node hot add may fail to update the cpu and node
masks of the top cpuset to include the newly added cpu or node in a
cgroup v2 environment.
For systems with cgroup v1 setup, cpuset_bind() is called again by
rebind_subsystem() when the v1 cpuset filesystem is mounted as shown
in the dmesg log below with an instrumented kernel.
[ 2.609781] cpuset_bind() called - v2 = 1
[ 3.079473] cpuset_init_smp() called
[ 7.103710] cpuset_bind() called - v2 = 0
smp_init() is called after the first two init functions. So we don't
have a complete list of active cpus and memory nodes until later in
cpuset_init_smp() which is the right time to set up effective_cpus
and effective_mems.
To fix this cgroup v2 mask setup problem, the potentially incorrect
cpus_allowed & mems_allowed setting in cpuset_init_smp() are removed.
For cgroup v2 systems, the initial cpuset_bind() call will set the masks
correctly. For cgroup v1 systems, the second call to cpuset_bind()
will do the right setup.
cc: stable@vger.kernel.org
Signed-off-by: Waiman Long <longman@redhat.com>
Tested-by: Feng Tang <feng.tang@intel.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
A kernel hang can be observed when running setserial in a loop on a kernel
with force threaded interrupts. The sequence of events is:
setserial
open("/dev/ttyXXX")
request_irq()
do_stuff()
-> serial interrupt
-> wake(irq_thread)
desc->threads_active++;
close()
free_irq()
kthread_stop(irq_thread)
synchronize_irq() <- hangs because desc->threads_active != 0
The thread is created in request_irq() and woken up, but does not get on a
CPU to reach the actual thread function, which would handle the pending
wake-up. kthread_stop() sets the should stop condition which makes the
thread immediately exit, which in turn leaves the stale threads_active
count around.
This problem was introduced with commit 519cc8652b, which addressed a
interrupt sharing issue in the PCIe code.
Before that commit free_irq() invoked synchronize_irq(), which waits for
the hard interrupt handler and also for associated threads to complete.
To address the PCIe issue synchronize_irq() was replaced with
__synchronize_hardirq(), which only waits for the hard interrupt handler to
complete, but not for threaded handlers.
This was done under the assumption, that the interrupt thread already
reached the thread function and waits for a wake-up, which is guaranteed to
be handled before acting on the stop condition. The problematic case, that
the thread would not reach the thread function, was obviously overlooked.
Make sure that the interrupt thread is really started and reaches
thread_fn() before returning from __setup_irq().
This utilizes the existing wait queue in the interrupt descriptor. The
wait queue is unused for non-shared interrupts. For shared interrupts the
usage might cause a spurious wake-up of a waiter in synchronize_irq() or the
completion of a threaded handler might cause a spurious wake-up of the
waiter for the ready flag. Both are harmless and have no functional impact.
[ tglx: Amended changelog ]
Fixes: 519cc8652b ("genirq: Synchronize only with single thread on free_irq()")
Signed-off-by: Thomas Pfaff <tpfaff@pcs.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/552fe7b4-9224-b183-bb87-a8f36d335690@pcs.com
The PASID is being freed too early. It needs to stay around until after
device drivers that might be using it have had a chance to clear it out
of the hardware.
The relevant refcounts are:
mmget() /mmput() refcount the mm's address space
mmgrab()/mmdrop() refcount the mm itself
The PASID is currently tied to the life of the mm's address space and freed
in __mmput(). This makes logical sense because the PASID can't be used
once the address space is gone.
But, this misses an important point: even after the address space is gone,
the PASID will still be programmed into a device. Device drivers might,
for instance, still need to flush operations that are outstanding and need
to use that PASID. They do this at file->release() time.
Device drivers call the IOMMU driver to hold a reference on the mm itself
and drop it at file->release() time. But, the IOMMU driver holds a
reference on the mm itself, not the address space. The address space (and
the PASID) is long gone by the time the driver tries to clean up. This is
effectively a use-after-free bug on the PASID.
To fix this, move the PASID free operation from __mmput() to __mmdrop().
This ensures that the IOMMU driver's existing mmgrab() keeps the PASID
allocated until it drops its mm reference.
Fixes: 701fac4038 ("iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit")
Reported-by: Zhangfei Gao <zhangfei.gao@foxmail.com>
Suggested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Suggested-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Zhangfei Gao <zhangfei.gao@foxmail.com>
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20220428180041.806809-1-fenghua.yu@intel.com
Pull networking fixes from Jakub Kicinski:
"Including fixes from bluetooth, bpf and netfilter.
Current release - new code bugs:
- bridge: switchdev: check br_vlan_group() return value
- use this_cpu_inc() to increment net->core_stats, fix preempt-rt
Previous releases - regressions:
- eth: stmmac: fix write to sgmii_adapter_base
Previous releases - always broken:
- netfilter: nf_conntrack_tcp: re-init for syn packets only,
resolving issues with TCP fastopen
- tcp: md5: fix incorrect tcp_header_len for incoming connections
- tcp: fix F-RTO may not work correctly when receiving DSACK
- tcp: ensure use of most recently sent skb when filling rate samples
- tcp: fix potential xmit stalls caused by TCP_NOTSENT_LOWAT
- virtio_net: fix wrong buf address calculation when using xdp
- xsk: fix forwarding when combining copy mode with busy poll
- xsk: fix possible crash when multiple sockets are created
- bpf: lwt: fix crash when using bpf_skb_set_tunnel_key() from
bpf_xmit lwt hook
- sctp: null-check asoc strreset_chunk in sctp_generate_reconf_event
- wireguard: device: check for metadata_dst with skb_valid_dst()
- netfilter: update ip6_route_me_harder to consider L3 domain
- gre: make o_seqno start from 0 in native mode
- gre: switch o_seqno to atomic to prevent races in collect_md mode
Misc:
- add Eric Dumazet to networking maintainers
- dt: dsa: realtek: remove realtek,rtl8367s string
- netfilter: flowtable: Remove the empty file"
* tag 'net-5.18-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (65 commits)
tcp: fix F-RTO may not work correctly when receiving DSACK
Revert "ibmvnic: Add ethtool private flag for driver-defined queue limits"
net: enetc: allow tc-etf offload even with NETIF_F_CSUM_MASK
ixgbe: ensure IPsec VF<->PF compatibility
MAINTAINERS: Update BNXT entry with firmware files
netfilter: nft_socket: only do sk lookups when indev is available
net: fec: add missing of_node_put() in fec_enet_init_stop_mode()
bnx2x: fix napi API usage sequence
tls: Skip tls_append_frag on zero copy size
Add Eric Dumazet to networking maintainers
netfilter: conntrack: fix udp offload timeout sysctl
netfilter: nf_conntrack_tcp: re-init for syn packets only
net: dsa: lantiq_gswip: Don't set GSWIP_MII_CFG_RMII_CLK
net: Use this_cpu_inc() to increment net->core_stats
Bluetooth: hci_sync: Cleanup hci_conn if it cannot be aborted
Bluetooth: hci_event: Fix creating hci_conn object on error status
Bluetooth: hci_event: Fix checking for invalid handle on error status
ice: fix use-after-free when deinitializing mailbox snapshot
ice: wait 5 s for EMP reset after firmware flash
ice: Protect vf_state check by cfg_lock in ice_vc_process_vf_msg()
...
Daniel Borkmann says:
====================
pull-request: bpf-next 2022-04-27
We've added 85 non-merge commits during the last 18 day(s) which contain
a total of 163 files changed, 4499 insertions(+), 1521 deletions(-).
The main changes are:
1) Teach libbpf to enhance BPF verifier log with human-readable and relevant
information about failed CO-RE relocations, from Andrii Nakryiko.
2) Add typed pointer support in BPF maps and enable it for unreferenced pointers
(via probe read) and referenced ones that can be passed to in-kernel helpers,
from Kumar Kartikeya Dwivedi.
3) Improve xsk to break NAPI loop when rx queue gets full to allow for forward
progress to consume descriptors, from Maciej Fijalkowski & Björn Töpel.
4) Fix a small RCU read-side race in BPF_PROG_RUN routines which dereferenced
the effective prog array before the rcu_read_lock, from Stanislav Fomichev.
5) Implement BPF atomic operations for RV64 JIT, and add libbpf parsing logic
for USDT arguments under riscv{32,64}, from Pu Lehui.
6) Implement libbpf parsing of USDT arguments under aarch64, from Alan Maguire.
7) Enable bpftool build for musl and remove nftw with FTW_ACTIONRETVAL usage
so it can be shipped under Alpine which is musl-based, from Dominique Martinet.
8) Clean up {sk,task,inode} local storage trace RCU handling as they do not
need to use call_rcu_tasks_trace() barrier, from KP Singh.
9) Improve libbpf API documentation and fix error return handling of various
API functions, from Grant Seltzer.
10) Enlarge offset check for bpf_skb_{load,store}_bytes() helpers given data
length of frags + frag_list may surpass old offset limit, from Liu Jian.
11) Various improvements to prog_tests in area of logging, test execution
and by-name subtest selection, from Mykola Lysenko.
12) Simplify map_btf_id generation for all map types by moving this process
to build time with help of resolve_btfids infra, from Menglong Dong.
13) Fix a libbpf bug in probing when falling back to legacy bpf_probe_read*()
helpers; the probing caused always to use old helpers, from Runqing Yang.
14) Add support for ARCompact and ARCv2 platforms for libbpf's PT_REGS
tracing macros, from Vladimir Isaev.
15) Cleanup BPF selftests to remove old & unneeded rlimit code given kernel
switched to memcg-based memory accouting a while ago, from Yafang Shao.
16) Refactor of BPF sysctl handlers to move them to BPF core, from Yan Zhu.
17) Fix BPF selftests in two occasions to work around regressions caused by latest
LLVM to unblock CI until their fixes are worked out, from Yonghong Song.
18) Misc cleanups all over the place, from various others.
* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (85 commits)
selftests/bpf: Add libbpf's log fixup logic selftests
libbpf: Fix up verifier log for unguarded failed CO-RE relos
libbpf: Simplify bpf_core_parse_spec() signature
libbpf: Refactor CO-RE relo human description formatting routine
libbpf: Record subprog-resolved CO-RE relocations unconditionally
selftests/bpf: Add CO-RE relos and SEC("?...") to linked_funcs selftests
libbpf: Avoid joining .BTF.ext data with BPF programs by section name
libbpf: Fix logic for finding matching program for CO-RE relocation
libbpf: Drop unhelpful "program too large" guess
libbpf: Fix anonymous type check in CO-RE logic
bpf: Compute map_btf_id during build time
selftests/bpf: Add test for strict BTF type check
selftests/bpf: Add verifier tests for kptr
selftests/bpf: Add C tests for kptr
libbpf: Add kptr type tag macros to bpf_helpers.h
bpf: Make BTF type match stricter for release arguments
bpf: Teach verifier about kptr_get kfunc helpers
bpf: Wire up freeing of referenced kptr
bpf: Populate pairs of btf_id and destructor kfunc in btf
bpf: Adapt copy_map_value for multiple offset case
...
====================
Link: https://lore.kernel.org/r/20220427224758.20976-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Daniel Borkmann says:
====================
pull-request: bpf 2022-04-27
We've added 5 non-merge commits during the last 20 day(s) which contain
a total of 6 files changed, 34 insertions(+), 12 deletions(-).
The main changes are:
1) Fix xsk sockets when rx and tx are separately bound to the same umem, also
fix xsk copy mode combined with busy poll, from Maciej Fijalkowski.
2) Fix BPF tunnel/collect_md helpers with bpf_xmit lwt hook usage which triggered
a crash due to invalid metadata_dst access, from Eyal Birger.
3) Fix release of page pool in XDP live packet mode, from Toke Høiland-Jørgensen.
4) Fix potential NULL pointer dereference in kretprobes, from Adam Zabrocki.
(Masami & Steven preferred this small fix to be routed via bpf tree given it's
follow-up fix to Masami's rethook work that went via bpf earlier, too.)
* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf:
xsk: Fix possible crash when multiple sockets are created
kprobes: Fix KRETPROBES when CONFIG_KRETPROBE_ON_RETHOOK is set
bpf, lwt: Fix crash when using bpf_skb_set_tunnel_key() from bpf_xmit lwt hook
bpf: Fix release of page_pool in BPF_PROG_RUN in test runner
xsk: Fix l2fwd for copy mode + busy poll combo
====================
Link: https://lore.kernel.org/r/20220427212748.9576-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
For now, the field 'map_btf_id' in 'struct bpf_map_ops' for all map
types are computed during vmlinux-btf init:
btf_parse_vmlinux() -> btf_vmlinux_map_ids_init()
It will lookup the btf_type according to the 'map_btf_name' field in
'struct bpf_map_ops'. This process can be done during build time,
thanks to Jiri's resolve_btfids.
selftest of map_ptr has passed:
$96 map_ptr:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The recent kernel change in 73f9b911fa ("kprobes: Use rethook for kretprobe
if possible"), introduced a potential NULL pointer dereference bug in the
KRETPROBE mechanism. The official Kprobes documentation defines that "Any or
all handlers can be NULL". Unfortunately, there is a missing return handler
verification to fulfill these requirements and can result in a NULL pointer
dereference bug.
This patch adds such verification in kretprobe_rethook_handler() function.
Fixes: 73f9b911fa ("kprobes: Use rethook for kretprobe if possible")
Signed-off-by: Adam Zabrocki <pi3@pi3.com.pl>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Anil S. Keshavamurthy <anil.s.keshavamurthy@intel.com>
Link: https://lore.kernel.org/bpf/20220422164027.GA7862@pi3.com.pl
The current of behavior of btf_struct_ids_match for release arguments is
that when type match fails, it retries with first member type again
(recursively). Since the offset is already 0, this is akin to just
casting the pointer in normal C, since if type matches it was just
embedded inside parent sturct as an object. However, we want to reject
cases for release function type matching, be it kfunc or BPF helpers.
An example is the following:
struct foo {
struct bar b;
};
struct foo *v = acq_foo();
rel_bar(&v->b); // btf_struct_ids_match fails btf_types_are_same, then
// retries with first member type and succeeds, while
// it should fail.
Hence, don't walk the struct and only rely on btf_types_are_same for
strict mode. All users of strict mode must be dealing with zero offset
anyway, since otherwise they would want the struct to be walked.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-10-memxor@gmail.com
We introduce a new style of kfunc helpers, namely *_kptr_get, where they
take pointer to the map value which points to a referenced kernel
pointer contained in the map. Since this is referenced, only
bpf_kptr_xchg from BPF side and xchg from kernel side is allowed to
change the current value, and each pointer that resides in that location
would be referenced, and RCU protected (this must be kept in mind while
adding kernel types embeddable as reference kptr in BPF maps).
This means that if do the load of the pointer value in an RCU read
section, and find a live pointer, then as long as we hold RCU read lock,
it won't be freed by a parallel xchg + release operation. This allows us
to implement a safe refcount increment scheme. Hence, enforce that first
argument of all such kfunc is a proper PTR_TO_MAP_VALUE pointing at the
right offset to referenced pointer.
For the rest of the arguments, they are subjected to typical kfunc
argument checks, hence allowing some flexibility in passing more intent
into how the reference should be taken.
For instance, in case of struct nf_conn, it is not freed until RCU grace
period ends, but can still be reused for another tuple once refcount has
dropped to zero. Hence, a bpf_ct_kptr_get helper not only needs to call
refcount_inc_not_zero, but also do a tuple match after incrementing the
reference, and when it fails to match it, put the reference again and
return NULL.
This can be implemented easily if we allow passing additional parameters
to the bpf_ct_kptr_get kfunc, like a struct bpf_sock_tuple * and a
tuple__sz pair.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-9-memxor@gmail.com
A destructor kfunc can be defined as void func(type *), where type may
be void or any other pointer type as per convenience.
In this patch, we ensure that the type is sane and capture the function
pointer into off_desc of ptr_off_tab for the specific pointer offset,
with the invariant that the dtor pointer is always set when 'kptr_ref'
tag is applied to the pointer's pointee type, which is indicated by the
flag BPF_MAP_VALUE_OFF_F_REF.
Note that only BTF IDs whose destructor kfunc is registered, thus become
the allowed BTF IDs for embedding as referenced kptr. Hence it serves
the purpose of finding dtor kfunc BTF ID, as well acting as a check
against the whitelist of allowed BTF IDs for this purpose.
Finally, wire up the actual freeing of the referenced pointer if any at
all available offsets, so that no references are leaked after the BPF
map goes away and the BPF program previously moved the ownership a
referenced pointer into it.
The behavior is similar to BPF timers, where bpf_map_{update,delete}_elem
will free any existing referenced kptr. The same case is with LRU map's
bpf_lru_push_free/htab_lru_push_free functions, which are extended to
reset unreferenced and free referenced kptr.
Note that unlike BPF timers, kptr is not reset or freed when map uref
drops to zero.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-8-memxor@gmail.com
To support storing referenced PTR_TO_BTF_ID in maps, we require
associating a specific BTF ID with a 'destructor' kfunc. This is because
we need to release a live referenced pointer at a certain offset in map
value from the map destruction path, otherwise we end up leaking
resources.
Hence, introduce support for passing an array of btf_id, kfunc_btf_id
pairs that denote a BTF ID and its associated release function. Then,
add an accessor 'btf_find_dtor_kfunc' which can be used to look up the
destructor kfunc of a certain BTF ID. If found, we can use it to free
the object from the map free path.
The registration of these pairs also serve as a whitelist of structures
which are allowed as referenced PTR_TO_BTF_ID in a BPF map, because
without finding the destructor kfunc, we will bail and return an error.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-7-memxor@gmail.com
Since now there might be at most 10 offsets that need handling in
copy_map_value, the manual shuffling and special case is no longer going
to work. Hence, let's generalise the copy_map_value function by using
a sorted array of offsets to skip regions that must be avoided while
copying into and out of a map value.
When the map is created, we populate the offset array in struct map,
Then, copy_map_value uses this sorted offset array is used to memcpy
while skipping timer, spin lock, and kptr. The array is allocated as
in most cases none of these special fields would be present in map
value, hence we can save on space for the common case by not embedding
the entire object inside bpf_map struct.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-6-memxor@gmail.com
While we can guarantee that even for unreferenced kptr, the object
pointer points to being freed etc. can be handled by the verifier's
exception handling (normal load patching to PROBE_MEM loads), we still
cannot allow the user to pass these pointers to BPF helpers and kfunc,
because the same exception handling won't be done for accesses inside
the kernel. The same is true if a referenced pointer is loaded using
normal load instruction. Since the reference is not guaranteed to be
held while the pointer is used, it must be marked as untrusted.
Hence introduce a new type flag, PTR_UNTRUSTED, which is used to mark
all registers loading unreferenced and referenced kptr from BPF maps,
and ensure they can never escape the BPF program and into the kernel by
way of calling stable/unstable helpers.
In check_ptr_to_btf_access, the !type_may_be_null check to reject type
flags is still correct, as apart from PTR_MAYBE_NULL, only MEM_USER,
MEM_PERCPU, and PTR_UNTRUSTED may be set for PTR_TO_BTF_ID. The first
two are checked inside the function and rejected using a proper error
message, but we still want to allow dereference of untrusted case.
Also, we make sure to inherit PTR_UNTRUSTED when chain of pointers are
walked, so that this flag is never dropped once it has been set on a
PTR_TO_BTF_ID (i.e. trusted to untrusted transition can only be in one
direction).
In convert_ctx_accesses, extend the switch case to consider untrusted
PTR_TO_BTF_ID in addition to normal PTR_TO_BTF_ID for PROBE_MEM
conversion for BPF_LDX.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-5-memxor@gmail.com
Extending the code in previous commits, introduce referenced kptr
support, which needs to be tagged using 'kptr_ref' tag instead. Unlike
unreferenced kptr, referenced kptr have a lot more restrictions. In
addition to the type matching, only a newly introduced bpf_kptr_xchg
helper is allowed to modify the map value at that offset. This transfers
the referenced pointer being stored into the map, releasing the
references state for the program, and returning the old value and
creating new reference state for the returned pointer.
Similar to unreferenced pointer case, return value for this case will
also be PTR_TO_BTF_ID_OR_NULL. The reference for the returned pointer
must either be eventually released by calling the corresponding release
function, otherwise it must be transferred into another map.
It is also allowed to call bpf_kptr_xchg with a NULL pointer, to clear
the value, and obtain the old value if any.
BPF_LDX, BPF_STX, and BPF_ST cannot access referenced kptr. A future
commit will permit using BPF_LDX for such pointers, but attempt at
making it safe, since the lifetime of object won't be guaranteed.
There are valid reasons to enforce the restriction of permitting only
bpf_kptr_xchg to operate on referenced kptr. The pointer value must be
consistent in face of concurrent modification, and any prior values
contained in the map must also be released before a new one is moved
into the map. To ensure proper transfer of this ownership, bpf_kptr_xchg
returns the old value, which the verifier would require the user to
either free or move into another map, and releases the reference held
for the pointer being moved in.
In the future, direct BPF_XCHG instruction may also be permitted to work
like bpf_kptr_xchg helper.
Note that process_kptr_func doesn't have to call
check_helper_mem_access, since we already disallow rdonly/wronly flags
for map, which is what check_map_access_type checks, and we already
ensure the PTR_TO_MAP_VALUE refers to kptr by obtaining its off_desc,
so check_map_access is also not required.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-4-memxor@gmail.com
Add a new type flag for bpf_arg_type that when set tells verifier that
for a release function, that argument's register will be the one for
which meta.ref_obj_id will be set, and which will then be released
using release_reference. To capture the regno, introduce a new field
release_regno in bpf_call_arg_meta.
This would be required in the next patch, where we may either pass NULL
or a refcounted pointer as an argument to the release function
bpf_kptr_xchg. Just releasing only when meta.ref_obj_id is set is not
enough, as there is a case where the type of argument needed matches,
but the ref_obj_id is set to 0. Hence, we must enforce that whenever
meta.ref_obj_id is zero, the register that is to be released can only
be NULL for a release function.
Since we now indicate whether an argument is to be released in
bpf_func_proto itself, is_release_function helper has lost its utitlity,
hence refactor code to work without it, and just rely on
meta.release_regno to know when to release state for a ref_obj_id.
Still, the restriction of one release argument and only one ref_obj_id
passed to BPF helper or kfunc remains. This may be lifted in the future.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-3-memxor@gmail.com
This commit introduces a new pointer type 'kptr' which can be embedded
in a map value to hold a PTR_TO_BTF_ID stored by a BPF program during
its invocation. When storing such a kptr, BPF program's PTR_TO_BTF_ID
register must have the same type as in the map value's BTF, and loading
a kptr marks the destination register as PTR_TO_BTF_ID with the correct
kernel BTF and BTF ID.
Such kptr are unreferenced, i.e. by the time another invocation of the
BPF program loads this pointer, the object which the pointer points to
may not longer exist. Since PTR_TO_BTF_ID loads (using BPF_LDX) are
patched to PROBE_MEM loads by the verifier, it would safe to allow user
to still access such invalid pointer, but passing such pointers into
BPF helpers and kfuncs should not be permitted. A future patch in this
series will close this gap.
The flexibility offered by allowing programs to dereference such invalid
pointers while being safe at runtime frees the verifier from doing
complex lifetime tracking. As long as the user may ensure that the
object remains valid, it can ensure data read by it from the kernel
object is valid.
The user indicates that a certain pointer must be treated as kptr
capable of accepting stores of PTR_TO_BTF_ID of a certain type, by using
a BTF type tag 'kptr' on the pointed to type of the pointer. Then, this
information is recorded in the object BTF which will be passed into the
kernel by way of map's BTF information. The name and kind from the map
value BTF is used to look up the in-kernel type, and the actual BTF and
BTF ID is recorded in the map struct in a new kptr_off_tab member. For
now, only storing pointers to structs is permitted.
An example of this specification is shown below:
#define __kptr __attribute__((btf_type_tag("kptr")))
struct map_value {
...
struct task_struct __kptr *task;
...
};
Then, in a BPF program, user may store PTR_TO_BTF_ID with the type
task_struct into the map, and then load it later.
Note that the destination register is marked PTR_TO_BTF_ID_OR_NULL, as
the verifier cannot know whether the value is NULL or not statically, it
must treat all potential loads at that map value offset as loading a
possibly NULL pointer.
Only BPF_LDX, BPF_STX, and BPF_ST (with insn->imm = 0 to denote NULL)
are allowed instructions that can access such a pointer. On BPF_LDX, the
destination register is updated to be a PTR_TO_BTF_ID, and on BPF_STX,
it is checked whether the source register type is a PTR_TO_BTF_ID with
same BTF type as specified in the map BTF. The access size must always
be BPF_DW.
For the map in map support, the kptr_off_tab for outer map is copied
from the inner map's kptr_off_tab. It was chosen to do a deep copy
instead of introducing a refcount to kptr_off_tab, because the copy only
needs to be done when paramterizing using inner_map_fd in the map in map
case, hence would be unnecessary for all other users.
It is not permitted to use MAP_FREEZE command and mmap for BPF map
having kptrs, similar to the bpf_timer case. A kptr also requires that
BPF program has both read and write access to the map (hence both
BPF_F_RDONLY_PROG and BPF_F_WRONLY_PROG are disallowed).
Note that check_map_access must be called from both
check_helper_mem_access and for the BPF instructions, hence the kptr
check must distinguish between ACCESS_DIRECT and ACCESS_HELPER, and
reject ACCESS_HELPER cases. We rename stack_access_src to bpf_access_src
and reuse it for this purpose.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220424214901.2743946-2-memxor@gmail.com
Rename bpf_prog_run_array_cg_flags to bpf_prog_run_array_cg and
use it everywhere. check_return_code already enforces sane
return ranges for all cgroup types. (only egress and bind hooks have
uncanonical return ranges, the rest is using [0, 1])
No functional changes.
v2:
- 'func_ret & 1' under explicit test (Andrii & Martin)
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220425220448.3669032-1-sdf@google.com
Pull scheduler fix from Borislav Petkov:
- Fix a corner case when calculating sched runqueue variables
That fix also removes a check for a zero divisor in the code, without
mentioning it. Vincent clarified that it's ok after I whined about it:
https://lore.kernel.org/all/CAKfTPtD2QEyZ6ADd5WrwETMOX0XOwJGnVddt7VHgfURdqgOS-Q@mail.gmail.com/
* tag 'sched_urgent_for_v5.18_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/pelt: Fix attach_entity_load_avg() corner case
