Commit 82b45e0a authored by Max Reitz's avatar Max Reitz
Browse files

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: default avatarDaniel P. Berrange <berrange@redhat.com>
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1549231


Cc: qemu-stable@nongnu.org
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Message-id: 20180228131315.30194-2-mreitz@redhat.com
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
parent 627f607e

block/file-posix.c

+3 −2
Original line number Diff line number Diff line
@@ -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");