[Qemu-commits] [qemu/qemu] 9fea27: linux-user: Fix llseek with high bit of offset_low...

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/qemu/qemu
  Commit: 9fea273c8511dd6e34138d028db774b031c0f70c
      
https://github.com/qemu/qemu/commit/9fea273c8511dd6e34138d028db774b031c0f70c
  Author: Peter Maydell <address@hidden>
  Date:   2016-08-16 (Tue, 16 Aug 2016)

  Changed paths:
    M linux-user/syscall.c

  Log Message:
  -----------
  linux-user: Fix llseek with high bit of offset_low set

The llseek syscall takes two 32-bit arguments, offset_high
and offset_low, which must be combined to form a single
64-bit offset. Unfortunately we were combining them with
   (uint64_t)arg2 << 32) | arg3
and arg3 is a signed type; this meant that when promoting
arg3 to a 64-bit type it would be sign-extended. The effect
was that if the offset happened to have bit 31 set then
this bit would get sign-extended into all of bits 63..32.
Explicitly cast arg3 to abi_ulong to avoid the erroneous
sign extension.

Reported-by: Chanho Park <address@hidden>
Signed-off-by: Peter Maydell <address@hidden>
Tested-by: Chanho Park <address@hidden>
Message-id: address@hidden