linux/include
Kees Cook 564c9cc84e locking/refcounts, x86/asm: Use unique .text section for refcount exceptions
Using .text.unlikely for refcount exceptions isn't safe because gcc may
move entire functions into .text.unlikely (e.g. in6_dev_dev()), which
would cause any uses of a protected refcount_t function to stay inline
with the function, triggering the protection unconditionally:

        .section        .text.unlikely,"ax",@progbits
        .type   in6_dev_get, @function
in6_dev_getx:
.LFB4673:
        .loc 2 4128 0
        .cfi_startproc
...
        lock; incl 480(%rbx)
        js 111f
        .pushsection .text.unlikely
111:    lea 480(%rbx), %rcx
112:    .byte 0x0f, 0xff
.popsection
113:

This creates a unique .text..refcount section and adds an additional
test to the exception handler to WARN in the case of having none of OF,
SF, nor ZF set so we can see things like this more easily in the future.

The double dot for the section name keeps it out of the TEXT_MAIN macro
namespace, to avoid collisions and so it can be put at the end with
text.unlikely to keep the cold code together.

See commit:

  cb87481ee8 ("kbuild: linker script do not match C names unless LD_DEAD_CODE_DATA_ELIMINATION is configured")

... which matches C names: [a-zA-Z0-9_] but not ".".

Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Elena <elena.reshetova@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch <linux-arch@vger.kernel.org>
Fixes: 7a46ec0e2f ("locking/refcounts, x86/asm: Implement fast refcount overflow protection")
Link: http://lkml.kernel.org/r/1504382986-49301-2-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-09-28 09:45:05 +02:00
..
acpi ACPI / bus: Make ACPI_HANDLE() work for non-GPL code again 2017-09-19 22:42:31 +02:00
asm-generic locking/refcounts, x86/asm: Use unique .text section for refcount exceptions 2017-09-28 09:45:05 +02:00
clocksource
crypto
drm lib/interval_tree: fast overlap detection 2017-09-08 18:26:49 -07:00
dt-bindings Merge branch '4.14-features' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2017-09-15 20:43:33 -07:00
keys net: rxrpc: Replace time_t type with time64_t type 2017-08-29 10:16:00 +01:00
kvm
linux Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2017-09-25 15:46:04 -07:00
math-emu
media media updates for v4.14-rc1 2017-09-07 12:53:14 -07:00
memory
misc
net net: prevent dst uses after free 2017-09-21 20:42:15 -07:00
pcmcia
ras
rdma More RDMA work and some op-structure constification from Chuck Lever, 2017-09-09 13:31:49 -07:00
scsi SCSI misc on 20170913 2017-09-13 10:47:14 -07:00
soc ARM: SoC driver updates for v4.14 2017-09-10 20:40:00 -07:00
sound sound updates for 4.14-rc1 2017-09-07 12:44:53 -07:00
target
trace Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-09-16 11:28:59 -07:00
uapi Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-09-23 05:41:27 -10:00
video
xen xen, arm64: drop dummy lookup_address() 2017-09-19 09:25:05 -04:00