From 361285886aa319a56c803f2fb783457f3e80f564 Mon Sep 17 00:00:00 2001 From: Anton Kolesov Date: Fri, 1 Aug 2014 22:18:47 +0400 Subject: lseek: Correct order of offset arguments 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 Signed-off-by: Bernhard Reutner-Fischer --- test/stdio/lseek_no_lfs.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) create mode 100644 test/stdio/lseek_no_lfs.c (limited to 'test') diff --git a/test/stdio/lseek_no_lfs.c b/test/stdio/lseek_no_lfs.c new file mode 100644 index 000000000..54daf6b48 --- /dev/null +++ b/test/stdio/lseek_no_lfs.c @@ -0,0 +1,22 @@ +#include +#include +#include + +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; +} -- cgit v1.2.3