From: Max Reitz <mre...@redhat.com> Storing the lseek() result in an int results in it overflowing when the file is at least 2 GB big. Then, we have a 50 % chance of the result being "negative" and thus thinking an error occurred when actually everything went just fine.
So we should use the correct type for storing the result: off_t. Reported-by: Daniel P. Berrange <berra...@redhat.com> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1549231 Cc: qemu-sta...@nongnu.org Signed-off-by: Max Reitz <mre...@redhat.com> Message-id: 20180228131315.30194-2-mre...@redhat.com Reviewed-by: Eric Blake <ebl...@redhat.com> Signed-off-by: Max Reitz <mre...@redhat.com> --- block/file-posix.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/block/file-posix.c b/block/file-posix.c index a2f6d8a8c8..3794c0007a 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1701,6 +1701,7 @@ static int raw_regular_truncate(int fd, int64_t offset, PreallocMode prealloc, case PREALLOC_MODE_FULL: { int64_t num = 0, left = offset - current_length; + off_t seek_result; /* * Knowing the final size from the beginning could allow the file @@ -1715,8 +1716,8 @@ static int raw_regular_truncate(int fd, int64_t offset, PreallocMode prealloc, buf = g_malloc0(65536); - result = lseek(fd, current_length, SEEK_SET); - if (result < 0) { + seek_result = lseek(fd, current_length, SEEK_SET); + if (seek_result < 0) { result = -errno; error_setg_errno(errp, -result, "Failed to seek to the old end of file"); -- 2.13.6
