From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45461) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1er1Y5-0000G6-UC for qemu-devel@nongnu.org; Wed, 28 Feb 2018 08:13:34 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1er1Y4-0001vn-Oz for qemu-devel@nongnu.org; Wed, 28 Feb 2018 08:13:33 -0500 From: Max Reitz Date: Wed, 28 Feb 2018 14:13:14 +0100 Message-Id: <20180228131315.30194-2-mreitz@redhat.com> In-Reply-To: <20180228131315.30194-1-mreitz@redhat.com> References: <20180228131315.30194-1-mreitz@redhat.com> Subject: [Qemu-devel] [PATCH 1/2] block/file-posix: Fix fully preallocated truncate List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, Max Reitz , Kevin Wolf , "Daniel P . Berrange" , qemu-stable@nongnu.org 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 --- 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 f1591c3849..90c25864a0 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1697,6 +1697,7 @@ 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 @@ -1711,8 +1712,8 @@ 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"); -- 2.14.3