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[libc] Fix integer overflow for large offsets in lseek. #162394

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Merged
merged 2 commits into from
Oct 8, 2025
Merged

[libc] Fix integer overflow for large offsets in lseek. #162394

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b1b84c6
[libc] Fix integer overflow for large offsets in lseek.
jtstogel Oct 7, 2025
1788205
Merge branch 'main' into fix-lseek-overflow
jtstogel Oct 8, 2025
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9 changes: 5 additions & 4 deletions libc/src/__support/File/linux/lseekImpl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -25,8 +25,9 @@ namespace internal {
LIBC_INLINE ErrorOr<off_t> lseekimpl(int fd, off_t offset, int whence) {
off_t result;
#ifdef SYS_lseek
int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_lseek, fd, offset, whence);
result = ret;
result = LIBC_NAMESPACE::syscall_impl<off_t>(SYS_lseek, fd, offset, whence);
if (result < 0)
return Error(-static_cast<int>(result));
#elif defined(SYS_llseek) || defined(SYS__llseek)
static_assert(sizeof(size_t) == 4, "size_t must be 32 bits.");
#ifdef SYS_llseek
Expand All @@ -37,11 +38,11 @@ LIBC_INLINE ErrorOr<off_t> lseekimpl(int fd, off_t offset, int whence) {
off_t offset_64 = offset;
int ret = LIBC_NAMESPACE::syscall_impl<int>(
LLSEEK_SYSCALL_NO, fd, offset_64 >> 32, offset_64, &result, whence);
if (ret < 0)
return Error(-ret);
#else
#error "lseek, llseek and _llseek syscalls not available."
#endif
if (ret < 0)
return Error(-ret);
return result;
}

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