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 time: 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.
Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
#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 */
}
--- /dev/null
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+
+int main(int argc, char *argv[])
+{
+ FILE * f = fopen(argv[0], "rb");
+ if (!f)
+ {
+ printf("Error: Can't open %s, reason: %s\n", argv[0], strerror(errno));
+ return 1;
+ }
+
+ if (fseek(f, (unsigned)4096, (int)SEEK_SET) == -1)
+ {
+ printf("Test failed, fseek return fail code. errno=%u (%s)\n", errno, strerror(errno));
+ return 1;
+ }
+
+ fclose(f);
+ return 0;
+}