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| author | John David Anglin <dave.anglin@bell.net> | 2017-11-12 01:11:16 +0300 |
|---|---|---|
| committer | Helge Deller <deller@gmx.de> | 2017-11-17 17:27:13 +0300 |
| commit | 05f016d2ca7a4fab99d5d5472168506ddf95e74f (patch) | |
| tree | d020d10f9e2c17fee084cd5471c36f957ded604c /arch/parisc | |
| parent | bebc6082da0a9f5d47a1ea2edc099bf671058bd4 (diff) | |
| download | linux-05f016d2ca7a4fab99d5d5472168506ddf95e74f.tar.xz | |
parisc: Fix validity check of pointer size argument in new CAS implementation
As noted by Christoph Biedl, passing a pointer size of 4 in the new CAS
implementation causes a kernel crash. The attached patch corrects the
off by one error in the argument validity check.
In reviewing the code, I noticed that we only perform word operations
with the pointer size argument. The subi instruction intentionally uses
a word condition on 64-bit kernels. Nullification was used instead of a
cmpib instruction as the branch should never be taken. The shlw
pseudo-operation generates a depw,z instruction and it clears the target
before doing a shift left word deposit. Thus, we don't need to clip the
upper 32 bits of this argument on 64-bit kernels.
Tested with a gcc testsuite run with a 64-bit kernel. The gcc atomic
code in libgcc is the only direct user of the new CAS implementation
that I am aware of.
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org # 3.13+
Signed-off-by: Helge Deller <deller@gmx.de>
Diffstat (limited to 'arch/parisc')
| -rw-r--r-- | arch/parisc/kernel/syscall.S | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index 41e60a9c7db2..e775f80ae28c 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -690,15 +690,15 @@ cas_action: /* ELF32 Process entry path */ lws_compare_and_swap_2: #ifdef CONFIG_64BIT - /* Clip the input registers */ + /* Clip the input registers. We don't need to clip %r23 as we + only use it for word operations */ depdi 0, 31, 32, %r26 depdi 0, 31, 32, %r25 depdi 0, 31, 32, %r24 - depdi 0, 31, 32, %r23 #endif /* Check the validity of the size pointer */ - subi,>>= 4, %r23, %r0 + subi,>>= 3, %r23, %r0 b,n lws_exit_nosys /* Jump to the functions which will load the old and new values into |