On 9 July 2014 17:06:46 Anton Kolesov <anton.kole...@synopsys.com> wrote:
There was a runtime error in systems without large file support. Call
fseek(fd, 4096, SEEK_SET) has been failing with EINVAL, though it was
succeeding for offset = 4092. This has been happening because llseek system
call accepts 64-bit value as an offset argument and lseek function has been
ordering 32-bits words that form this offset value, according to the
endianness. However this ordering to match endianness is not required,
because llseek doesn't accept one 64-bit offset argument, it accepts two
32-bit offset argument, then stitches them into one following its
endianness. As a result on little endian system, order of words has been
swapped two times: in libc and in kernel. Thus call to fseek with offset 4096
(0x1000) was doing a system call to llseek with offset 0x1000_0000_0000. I'm
not entirely sure why then offset = 4092 hasn't been failing then.
This patch removes malicious swap of words when calling llseek.
Please also add a test case.
TIA,
Signed-off-by: Anton Kolesov <anton.kole...@synopsys.com>
---
libc/sysdeps/linux/common/lseek.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/libc/sysdeps/linux/common/lseek.c
b/libc/sysdeps/linux/common/lseek.c
index 500c6bf..11a1fbb 100644
--- a/libc/sysdeps/linux/common/lseek.c
+++ b/libc/sysdeps/linux/common/lseek.c
@@ -24,9 +24,7 @@ off_t __NC(lseek)(int fd, off_t offset, int whence)
#elif __WORDSIZE == 32
__off64_t result;
__off_t high = 0;
- return INLINE_SYSCALL(llseek, 5, fd,
- __LONG_LONG_PAIR(high, offset),
- &result, whence) ?: result;
+ return INLINE_SYSCALL(llseek, 5, fd, high, offset, &result, whence) ?:
result;
#endif
/* No need to handle __WORDSIZE == 64 as such a kernel won't define
__NR_llseek */
}
--
1.8.4.1
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