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MIPS: Drop spurious __unused in struct compat_flock

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MIPS' struct compat_flock doesn't match the 32-bit struct flock, as it
has an extra short __unused before pad[4], which combined with alignment
increases the size to 40 bytes compared with struct flock's 36 bytes.

Since commit 8c6657cb50 ("Switch flock copyin/copyout primitives to
copy_{from,to}_user()"), put_compat_flock() writes the full compat_flock
struct to userland, which results in corruption of the userland word
after the struct flock when running 32-bit userlands on 64-bit kernels.

This was observed to cause a bus error exception when starting Firefox
on Debian 8 (Jessie).

Reported-by: Peter Mamonov <pmamonov@gmail.com>
Signed-off-by: James Hogan <jhogan@kernel.org>
Tested-by: Peter Mamonov <pmamonov@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # 4.13+
Patchwork: https://patchwork.linux-mips.org/patch/18646/
This commit is contained in:
James Hogan 2018-02-20 15:44:37 +00:00
parent 91ab883eb2
commit 6ae1756fad
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GPG key ID: 6C0B6993DE38767A
1 changed files with 0 additions and 1 deletions
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arch/mips/include/asm/compat.h
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@ -86,7 +86,6 @@ struct compat_flock {
compat_off_t l_len;
s32 l_sysid;
compat_pid_t l_pid;
short __unused;
s32 pad[4];
};