From: Max Reitz Date: Wed, 28 Feb 2018 13:13:14 +0000 (+0100) Subject: block/file-posix: Fix fully preallocated truncate X-Git-Tag: v2.11.2~75 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d315353bed0ee4f4a505b8c5fdf24dc63659ae92;p=thirdparty%2Fqemu.git block/file-posix: Fix fully preallocated truncate 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 Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1549231 Cc: qemu-stable@nongnu.org Signed-off-by: Max Reitz Message-id: 20180228131315.30194-2-mreitz@redhat.com Reviewed-by: Eric Blake Signed-off-by: Max Reitz (cherry picked from commit 82b45e0a0b824787bd79ce3f6453eaa2afddd138) Signed-off-by: Michael Roth --- diff --git a/block/file-posix.c b/block/file-posix.c index 36ee89e9402..275953fdc68 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1694,6 +1694,7 @@ 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 @@ -1708,8 +1709,8 @@ 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");