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

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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 <parkch98@gmail.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Chanho Park <parkch98@gmail.com>
Message-id: 1470938379-1133-1-git-send-email-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2016-08-11 18:59:39 +01:00
parent 9c37146782
commit 9fea273c85
1 changed files with 1 additions and 1 deletions
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2
linux-user/syscall.c
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@ -9389,7 +9389,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
{
int64_t res;
#if !defined(__NR_llseek)
res = lseek(arg1, ((uint64_t)arg2 << 32) | arg3, arg5);
res = lseek(arg1, ((uint64_t)arg2 << 32) | (abi_ulong)arg3, arg5);
if (res == -1) {
ret = get_errno(res);
} else {