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 8c6657cb50cb ("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@xxxxxxxxx>
Signed-off-by: James Hogan <jhogan@xxxxxxxxxx>
Tested-by: Peter Mamonov <pmamonov@xxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx> # 4.13+
---
Resend mainly so it lands in patchwork.
---
arch/mips/include/asm/compat.h | 1 -
1 file changed, 1 deletion(-)
diff --git a/arch/mips/include/asm/compat.h b/arch/mips/include/asm/compat.h
index 946681db8dc3..9a0fa66b81ac 100644
--- a/arch/mips/include/asm/compat.h
+++ b/arch/mips/include/asm/compat.h
@@ -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];
};
--
2.13.6