Commit Graph

54 Commits

Author SHA1 Message Date
Martin Wilck
1359798f9d string.h: un-fortify memcpy_and_pad
The way I'd implemented the new helper memcpy_and_pad  with
__FORTIFY_INLINE caused compiler warnings for certain kernel
configurations.

This helper is only used in a single place at this time, and thus
doesn't benefit much from fortification. So simplify the code
by dropping fortification support for now.

Fixes: 01f33c336e "string.h: add memcpy_and_pad()"
Signed-off-by: Martin Wilck <mwilck@suse.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2017-09-11 12:29:41 -04:00
Linus Torvalds
126e76ffbf Merge branch 'for-4.14/block-postmerge' of git://git.kernel.dk/linux-block
Pull followup block layer updates from Jens Axboe:
 "I ended up splitting the main pull request for this series into two,
  mainly because of clashes between NVMe fixes that went into 4.13 after
  the for-4.14 branches were split off. This pull request is mostly
  NVMe, but not exclusively. In detail, it contains:

   - Two pull request for NVMe changes from Christoph. Nothing new on
     the feature front, basically just fixes all over the map for the
     core bits, transport, rdma, etc.

   - Series from Bart, cleaning up various bits in the BFQ scheduler.

   - Series of bcache fixes, which has been lingering for a release or
     two. Coly sent this in, but patches from various people in this
     area.

   - Set of patches for BFQ from Paolo himself, updating both
     documentation and fixing some corner cases in performance.

   - Series from Omar, attempting to now get the 4k loop support
     correct. Our confidence level is higher this time.

   - Series from Shaohua for loop as well, improving O_DIRECT
     performance and fixing a use-after-free"

* 'for-4.14/block-postmerge' of git://git.kernel.dk/linux-block: (74 commits)
  bcache: initialize dirty stripes in flash_dev_run()
  loop: set physical block size to logical block size
  bcache: fix bch_hprint crash and improve output
  bcache: Update continue_at() documentation
  bcache: silence static checker warning
  bcache: fix for gc and write-back race
  bcache: increase the number of open buckets
  bcache: Correct return value for sysfs attach errors
  bcache: correct cache_dirty_target in __update_writeback_rate()
  bcache: gc does not work when triggering by manual command
  bcache: Don't reinvent the wheel but use existing llist API
  bcache: do not subtract sectors_to_gc for bypassed IO
  bcache: fix sequential large write IO bypass
  bcache: Fix leak of bdev reference
  block/loop: remove unused field
  block/loop: fix use after free
  bfq: Use icq_to_bic() consistently
  bfq: Suppress compiler warnings about comparisons
  bfq: Check kstrtoul() return value
  bfq: Declare local functions static
  ...
2017-09-09 12:49:01 -07:00
Matthew Wilcox
3b3c4babd8 lib/string.c: add multibyte memset functions
Patch series "Multibyte memset variations", v4.

A relatively common idiom we're missing is a function to fill an area of
memory with a pattern which is larger than a single byte.  I first
noticed this with a zram patch which wanted to fill a page with an
'unsigned long' value.  There turn out to be quite a few places in the
kernel which can benefit from using an optimised function rather than a
loop; sometimes text size, sometimes speed, and sometimes both.  The
optimised PowerPC version (not included here) improves performance by
about 30% on POWER8 on just the raw memset_l().

Most of the extra lines of code come from the three testcases I added.

This patch (of 8):

memset16(), memset32() and memset64() are like memset(), but allow the
caller to fill the destination with a value larger than a single byte.
memset_l() and memset_p() allow the caller to use unsigned long and
pointer values respectively.

Link: http://lkml.kernel.org/r/20170720184539.31609-2-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: David Miller <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-08 18:26:48 -07:00
Martin Wilck
01f33c336e string.h: add memcpy_and_pad()
This helper function is useful for the nvme subsystem, and maybe
others.

Note: the warnings reported by the kbuild test robot for this patch
are actually generated by the use of CONFIG_PROFILE_ALL_BRANCHES
together with __FORTIFY_INLINE.

Signed-off-by: Martin Wilck <mwilck@suse.com>
Reviewed-by: Sagi Grimberg <sagi@grimbeg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2017-08-28 23:00:41 +03:00
Linus Torvalds
78dcf73421 Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull ->s_options removal from Al Viro:
 "Preparations for fsmount/fsopen stuff (coming next cycle). Everything
  gets moved to explicit ->show_options(), killing ->s_options off +
  some cosmetic bits around fs/namespace.c and friends. Basically, the
  stuff needed to work with fsmount series with minimum of conflicts
  with other work.

  It's not strictly required for this merge window, but it would reduce
  the PITA during the coming cycle, so it would be nice to have those
  bits and pieces out of the way"

* 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  isofs: Fix isofs_show_options()
  VFS: Kill off s_options and helpers
  orangefs: Implement show_options
  9p: Implement show_options
  isofs: Implement show_options
  afs: Implement show_options
  affs: Implement show_options
  befs: Implement show_options
  spufs: Implement show_options
  bpf: Implement show_options
  ramfs: Implement show_options
  pstore: Implement show_options
  omfs: Implement show_options
  hugetlbfs: Implement show_options
  VFS: Don't use save/replace_mount_options if not using generic_show_options
  VFS: Provide empty name qstr
  VFS: Make get_filesystem() return the affected filesystem
  VFS: Clean up whitespace in fs/namespace.c and fs/super.c
  Provide a function to create a NUL-terminated string from unterminated data
2017-07-15 12:00:42 -07:00
Daniel Micay
077d2ba519 replace incorrect strscpy use in FORTIFY_SOURCE
Using strscpy was wrong because FORTIFY_SOURCE is passing the maximum
possible size of the outermost object, but strscpy defines the count
parameter as the exact buffer size, so this could copy past the end of
the source.  This would still be wrong with the planned usage of
__builtin_object_size(p, 1) for intra-object overflow checks since it's
the maximum possible size of the specified object with no guarantee of
it being that large.

Reuse of the fortified functions like this currently makes the runtime
error reporting less precise but that can be improved later on.

Noticed by Dave Jones and KASAN.

Signed-off-by: Daniel Micay <danielmicay@gmail.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reported-by: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-14 21:56:31 -07:00
Daniel Micay
6974f0c455 include/linux/string.h: add the option of fortified string.h functions
This adds support for compiling with a rough equivalent to the glibc
_FORTIFY_SOURCE=1 feature, providing compile-time and runtime buffer
overflow checks for string.h functions when the compiler determines the
size of the source or destination buffer at compile-time.  Unlike glibc,
it covers buffer reads in addition to writes.

GNU C __builtin_*_chk intrinsics are avoided because they would force a
much more complex implementation.  They aren't designed to detect read
overflows and offer no real benefit when using an implementation based
on inline checks.  Inline checks don't add up to much code size and
allow full use of the regular string intrinsics while avoiding the need
for a bunch of _chk functions and per-arch assembly to avoid wrapper
overhead.

This detects various overflows at compile-time in various drivers and
some non-x86 core kernel code.  There will likely be issues caught in
regular use at runtime too.

Future improvements left out of initial implementation for simplicity,
as it's all quite optional and can be done incrementally:

* Some of the fortified string functions (strncpy, strcat), don't yet
  place a limit on reads from the source based on __builtin_object_size of
  the source buffer.

* Extending coverage to more string functions like strlcat.

* It should be possible to optionally use __builtin_object_size(x, 1) for
  some functions (C strings) to detect intra-object overflows (like
  glibc's _FORTIFY_SOURCE=2), but for now this takes the conservative
  approach to avoid likely compatibility issues.

* The compile-time checks should be made available via a separate config
  option which can be enabled by default (or always enabled) once enough
  time has passed to get the issues it catches fixed.

Kees said:
 "This is great to have. While it was out-of-tree code, it would have
  blocked at least CVE-2016-3858 from being exploitable (improper size
  argument to strlcpy()). I've sent a number of fixes for
  out-of-bounds-reads that this detected upstream already"

[arnd@arndb.de: x86: fix fortified memcpy]
  Link: http://lkml.kernel.org/r/20170627150047.660360-1-arnd@arndb.de
[keescook@chromium.org: avoid panic() in favor of BUG()]
  Link: http://lkml.kernel.org/r/20170626235122.GA25261@beast
[keescook@chromium.org: move from -mm, add ARCH_HAS_FORTIFY_SOURCE, tweak Kconfig help]
Link: http://lkml.kernel.org/r/20170526095404.20439-1-danielmicay@gmail.com
Link: http://lkml.kernel.org/r/1497903987-21002-8-git-send-email-keescook@chromium.org
Signed-off-by: Daniel Micay <danielmicay@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Daniel Axtens <dja@axtens.net>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-12 16:26:03 -07:00
David Howells
f351574172 Provide a function to create a NUL-terminated string from unterminated data
Provide a function, kmemdup_nul(), that will create a NUL-terminated string
from an unterminated character array where the length is known in advance.

This is better than kstrndup() in situations where we already know the
string length as the strnlen() in kstrndup() is superfluous.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-07-06 03:27:09 -04:00
Dan Williams
0aed55af88 x86, uaccess: introduce copy_from_iter_flushcache for pmem / cache-bypass operations
The pmem driver has a need to transfer data with a persistent memory
destination and be able to rely on the fact that the destination writes are not
cached. It is sufficient for the writes to be flushed to a cpu-store-buffer
(non-temporal / "movnt" in x86 terms), as we expect userspace to call fsync()
to ensure data-writes have reached a power-fail-safe zone in the platform. The
fsync() triggers a REQ_FUA or REQ_FLUSH to the pmem driver which will turn
around and fence previous writes with an "sfence".

Implement a __copy_from_user_inatomic_flushcache, memcpy_page_flushcache, and
memcpy_flushcache, that guarantee that the destination buffer is not dirty in
the cpu cache on completion. The new copy_from_iter_flushcache and sub-routines
will be used to replace the "pmem api" (include/linux/pmem.h +
arch/x86/include/asm/pmem.h). The availability of copy_from_iter_flushcache()
and memcpy_flushcache() are gated by the CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
config symbol, and fallback to copy_from_iter_nocache() and plain memcpy()
otherwise.

This is meant to satisfy the concern from Linus that if a driver wants to do
something beyond the normal nocache semantics it should be something private to
that driver [1], and Al's concern that anything uaccess related belongs with
the rest of the uaccess code [2].

The first consumer of this interface is a new 'copy_from_iter' dax operation so
that pmem can inject cache maintenance operations without imposing this
overhead on other dax-capable drivers.

[1]: https://lists.01.org/pipermail/linux-nvdimm/2017-January/008364.html
[2]: https://lists.01.org/pipermail/linux-nvdimm/2017-April/009942.html

Cc: <x86@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
2017-06-09 09:09:56 -07:00
Linus Torvalds
53ef7d0e20 Merge tag 'libnvdimm-for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm
Pull libnvdimm updates from Dan Williams:
 "The bulk of this has been in multiple -next releases. There were a few
  late breaking fixes and small features that got added in the last
  couple days, but the whole set has received a build success
  notification from the kbuild robot.

  Change summary:

   - Region media error reporting: A libnvdimm region device is the
     parent to one or more namespaces. To date, media errors have been
     reported via the "badblocks" attribute attached to pmem block
     devices for namespaces in "raw" or "memory" mode. Given that
     namespaces can be in "device-dax" or "btt-sector" mode this new
     interface reports media errors generically, i.e. independent of
     namespace modes or state.

     This subsequently allows userspace tooling to craft "ACPI 6.1
     Section 9.20.7.6 Function Index 4 - Clear Uncorrectable Error"
     requests and submit them via the ioctl path for NVDIMM root bus
     devices.

   - Introduce 'struct dax_device' and 'struct dax_operations': Prompted
     by a request from Linus and feedback from Christoph this allows for
     dax capable drivers to publish their own custom dax operations.
     This fixes the broken assumption that all dax operations are
     related to a persistent memory device, and makes it easier for
     other architectures and platforms to add customized persistent
     memory support.

   - 'libnvdimm' core updates: A new "deep_flush" sysfs attribute is
     available for storage appliance applications to manually trigger
     memory controllers to drain write-pending buffers that would
     otherwise be flushed automatically by the platform ADR
     (asynchronous-DRAM-refresh) mechanism at a power loss event.
     Support for "locked" DIMMs is included to prevent namespaces from
     surfacing when the namespace label data area is locked. Finally,
     fixes for various reported deadlocks and crashes, also tagged for
     -stable.

   - ACPI / nfit driver updates: General updates of the nfit driver to
     add DSM command overrides, ACPI 6.1 health state flags support, DSM
     payload debug available by default, and various fixes.

  Acknowledgements that came after the branch was pushed:

   - commmit 565851c972 "device-dax: fix sysfs attribute deadlock":
     Tested-by: Yi Zhang <yizhan@redhat.com>

   - commit 23f4984483 "libnvdimm: rework region badblocks clearing"
     Tested-by: Toshi Kani <toshi.kani@hpe.com>"

* tag 'libnvdimm-for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm: (52 commits)
  libnvdimm, pfn: fix 'npfns' vs section alignment
  libnvdimm: handle locked label storage areas
  libnvdimm: convert NDD_ flags to use bitops, introduce NDD_LOCKED
  brd: fix uninitialized use of brd->dax_dev
  block, dax: use correct format string in bdev_dax_supported
  device-dax: fix sysfs attribute deadlock
  libnvdimm: restore "libnvdimm: band aid btt vs clear poison locking"
  libnvdimm: fix nvdimm_bus_lock() vs device_lock() ordering
  libnvdimm: rework region badblocks clearing
  acpi, nfit: kill ACPI_NFIT_DEBUG
  libnvdimm: fix clear length of nvdimm_forget_poison()
  libnvdimm, pmem: fix a NULL pointer BUG in nd_pmem_notify
  libnvdimm, region: sysfs trigger for nvdimm_flush()
  libnvdimm: fix phys_addr for nvdimm_clear_poison
  x86, dax, pmem: remove indirection around memcpy_from_pmem()
  block: remove block_device_operations ->direct_access()
  block, dax: convert bdev_dax_supported() to dax_direct_access()
  filesystem-dax: convert to dax_direct_access()
  Revert "block: use DAX for partition table reads"
  ext2, ext4, xfs: retrieve dax_device for iomap operations
  ...
2017-05-05 18:49:20 -07:00
Dan Williams
6abccd1bfe x86, dax, pmem: remove indirection around memcpy_from_pmem()
memcpy_from_pmem() maps directly to memcpy_mcsafe(). The wrapper
serves no real benefit aside from affording a more generic function name
than the x86-specific 'mcsafe'. However this would not be the first time
that x86 terminology leaked into the global namespace. For lack of
better name, just use memcpy_mcsafe() directly.

This conversion also catches a place where we should have been using
plain memcpy, acpi_nfit_blk_single_io().

Cc: <x86@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Acked-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
2017-04-25 13:20:46 -07:00
Heikki Krogerus
e1fe7b6a7b lib/string: add sysfs_match_string helper
Make a simple helper for matching strings with sysfs
attribute files. In most parts the same as match_string(),
except sysfs_match_string() uses sysfs_streq() instead of
strcmp() for matching. This is more convenient when used
with sysfs attributes.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-03-23 13:48:44 +01:00
Rasmus Villemoes
48a270554a include/linux: apply __malloc attribute
Attach the malloc attribute to a few allocation functions.  This helps
gcc generate better code by telling it that the return value doesn't
alias any existing pointers (which is even more valuable given the
pessimizations implied by -fno-strict-aliasing).

A simple example of what this allows gcc to do can be seen by looking at
the last part of drm_atomic_helper_plane_reset:

	plane->state = kzalloc(sizeof(*plane->state), GFP_KERNEL);

	if (plane->state) {
		plane->state->plane = plane;
		plane->state->rotation = BIT(DRM_ROTATE_0);
	}

which compiles to

    e8 99 bf d6 ff          callq  ffffffff8116d540 <kmem_cache_alloc_trace>
    48 85 c0                test   %rax,%rax
    48 89 83 40 02 00 00    mov    %rax,0x240(%rbx)
    74 11                   je     ffffffff814015c4 <drm_atomic_helper_plane_reset+0x64>
    48 89 18                mov    %rbx,(%rax)
    48 8b 83 40 02 00 00    mov    0x240(%rbx),%rax [*]
    c7 40 40 01 00 00 00    movl   $0x1,0x40(%rax)

With this patch applied, the instruction at [*] is elided, since the
store to plane->state->plane is known to not alter the value of
plane->state.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-19 19:12:14 -07:00
Kees Cook
ef95159907 lib: move strtobool() to kstrtobool()
Create the kstrtobool_from_user() helper and move strtobool() logic into
the new kstrtobool() (matching all the other kstrto* functions).
Provides an inline wrapper for existing strtobool() callers.

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Joe Perches <joe@perches.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Amitkumar Karwar <akarwar@marvell.com>
Cc: Nishant Sarmukadam <nishants@marvell.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: Steve French <sfrench@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-17 15:09:34 -07:00
Andy Shevchenko
56b060814e lib/string: introduce match_string() helper
Occasionally we have to search for an occurrence of a string in an array
of strings.  Make a simple helper for that purpose.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: David Airlie <airlied@linux.ie>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-17 15:09:34 -07:00
Al Viro
e9d408e107 new helper: memdup_user_nul()
Similar to memdup_user(), except that allocated buffer is one byte
longer and '\0' is stored after the copied data.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-01-04 10:20:19 -05:00
Chris Metcalf
30035e4575 string: provide strscpy()
The strscpy() API is intended to be used instead of strlcpy(),
and instead of most uses of strncpy().

- Unlike strlcpy(), it doesn't read from memory beyond (src + size).

- Unlike strlcpy() or strncpy(), the API provides an easy way to check
  for destination buffer overflow: an -E2BIG error return value.

- The provided implementation is robust in the face of the source
  buffer being asynchronously changed during the copy, unlike the
  current implementation of strlcpy().

- Unlike strncpy(), the destination buffer will be NUL-terminated
  if the string in the source buffer is too long.

- Also unlike strncpy(), the destination buffer will not be updated
  beyond the NUL termination, avoiding strncpy's behavior of zeroing
  the entire tail end of the destination buffer.  (A memset() after
  the strscpy() can be used if this behavior is desired.)

- The implementation should be reasonably performant on all
  platforms since it uses the asm/word-at-a-time.h API rather than
  simple byte copy.  Kernel-to-kernel string copy is not considered
  to be performance critical in any case.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
2015-09-10 15:36:59 -04:00
Rasmus Villemoes
94df290404 lib/string.c: introduce strreplace()
Strings are sometimes sanitized by replacing a certain character (often
'/') by another (often '!').  In a few places, this is done the same way
Schlemiel the Painter would do it.  Others are slightly smarter but still
do multiple strchr() calls.  Introduce strreplace() to do this using a
single function call and a single pass over the string.

One would expect the return value to be one of three things: void, s, or
the number of replacements made.  I chose the fourth, returning a pointer
to the end of the string.  This is more likely to be useful (for example
allowing the caller to avoid a strlen call).

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Neil Brown <neilb@suse.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-06-25 17:00:40 -07:00
Andrzej Hajda
a4bb1e43e2 mm/util: add kstrdup_const
kstrdup() is often used to duplicate strings where neither source neither
destination will be ever modified.  In such case we can just reuse the
source instead of duplicating it.  The problem is that we must be sure
that the source is non-modifiable and its life-time is long enough.

I suspect the good candidates for such strings are strings located in
kernel .rodata section, they cannot be modifed because the section is
read-only and their life-time is equal to kernel life-time.

This small patchset proposes alternative version of kstrdup -
kstrdup_const, which returns source string if it is located in .rodata
otherwise it fallbacks to kstrdup.  To verify if the source is in
.rodata function checks if the address is between sentinels
__start_rodata, __end_rodata.  I guess it should work with all
architectures.

The main patch is accompanied by four patches constifying kstrdup for
cases where situtation described above happens frequently.

I have tested the patchset on mobile platform (exynos4210-trats) and it
saves 3272 string allocations.  Since minimal allocation is 32 or 64
bytes depending on Kconfig options the patchset saves respectively about
100KB or 200KB of memory.

Stats from tested platform show that the main offender is sysfs:

By caller:
  2260 __kernfs_new_node
    631 clk_register+0xc8/0x1b8
    318 clk_register+0x34/0x1b8
      51 kmem_cache_create
      12 alloc_vfsmnt

By string (with count >= 5):
    883 power
    876 subsystem
    135 parameters
    132 device
     61 iommu_group
    ...

This patch (of 5):

Add an alternative version of kstrdup which returns pointer to constant
char array.  The function checks if input string is in persistent and
read-only memory section, if yes it returns the input string, otherwise it
fallbacks to kstrdup.

kstrdup_const is accompanied by kfree_const performing conditional memory
deallocation of the string.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Greg KH <greg@kroah.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-13 21:21:35 -08:00
Rasmus Villemoes
af3cd13501 lib/string.c: remove strnicmp()
Now that all in-tree users of strnicmp have been converted to
strncasecmp, the wrapper can be removed.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: David Howells <dhowells@redhat.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-12 18:54:14 -08:00
Linus Torvalds
14d4cc0883 Merge tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random
Pull /dev/random updates from Ted Ts'o:
 "This adds a memzero_explicit() call which is guaranteed not to be
  optimized away by GCC.  This is important when we are wiping
  cryptographically sensitive material"

* tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  crypto: memzero_explicit - make sure to clear out sensitive data
  random: add and use memzero_explicit() for clearing data
2014-10-24 12:33:32 -07:00
Daniel Borkmann
d4c5efdb97 random: add and use memzero_explicit() for clearing data
zatimend has reported that in his environment (3.16/gcc4.8.3/corei7)
memset() calls which clear out sensitive data in extract_{buf,entropy,
entropy_user}() in random driver are being optimized away by gcc.

Add a helper memzero_explicit() (similarly as explicit_bzero() variants)
that can be used in such cases where a variable with sensitive data is
being cleared out in the end. Other use cases might also be in crypto
code. [ I have put this into lib/string.c though, as it's always built-in
and doesn't need any dependencies then. ]

Fixes kernel bugzilla: 82041

Reported-by: zatimend@hotmail.co.uk
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
2014-10-17 11:37:29 -04:00
Rasmus Villemoes
b0bfb63118 lib: string: Make all calls to strnicmp into calls to strncasecmp
The previous patch made strnicmp into a wrapper for strncasecmp.

This patch makes all in-tree users of strnicmp call strncasecmp
directly, while still making sure that the strnicmp symbol can be used
by out-of-tree modules.  It should be considered a temporary hack until
all in-tree callers have been converted.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-10-14 02:18:23 +02:00
Grant Likely
11d200e95f lib: add glibc style strchrnul() variant
The strchrnul() variant helpfully returns a the end of the string
instead of a NULL if the requested character is not found. This can
simplify string parsing code since it doesn't need to expicitly check
for a NULL return. If a valid string pointer is passed in, then a valid
null terminated string will always come back out.

Signed-off-by: Grant Likely <grant.likely@linaro.org>
2014-05-23 11:23:27 +09:00
Andy Shevchenko
b18888ab25 string: introduce helper to get base file name from given path
There are several places in the kernel that use functionality like
basename(3) with the exception: in case of '/foo/bar/' we expect to get an
empty string.  Let's do it common helper for them.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: YAMANE Toshiaki <yamanetoshi@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-17 17:15:17 -08:00