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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 <berrange@redhat.com>
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1549231
Cc: qemu-stable@nongnu.org
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20180228131315.30194-2-mreitz@redhat.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
(cherry picked from commit 82b45e0a0b)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
stable-2.11
Max Reitz 2018-02-28 14:13:14 +01:00 committed by Michael Roth
parent 332969a64d
commit d315353bed
1 changed files with 3 additions and 2 deletions
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5
block/file-posix.c
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@ -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");