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block/cow: Avoid use of uninitialized cow_bs in error path

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Commit 25814e8987 introduced an error-exit code path which does
a "goto exit" before the cow_bs variable is initialized, meaning
we would call bdrv_unref() on an uninitialized variable and
likely segfault. Fix this by moving the NULL-initialization
to the top of the function and making the exit code path handle
the case where it is NULL.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Peter Maydell 2014-06-30 19:03:37 +01:00 committed by Stefan Hajnoczi
parent 4caf0fcd45
commit 6764579f89
1 changed files with 4 additions and 3 deletions
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7
block/cow.c
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@ -332,7 +332,7 @@ static int cow_create(const char *filename, QemuOpts *opts, Error **errp)
char *image_filename = NULL;
Error *local_err = NULL;
int ret;
BlockDriverState *cow_bs;
BlockDriverState *cow_bs = NULL;
/* Read out options */
image_sectors = qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0) / 512;
@ -344,7 +344,6 @@ static int cow_create(const char *filename, QemuOpts *opts, Error **errp)
goto exit;
}
cow_bs = NULL;
ret = bdrv_open(&cow_bs, filename, NULL, NULL,
BDRV_O_RDWR | BDRV_O_PROTOCOL, NULL, &local_err);
if (ret < 0) {
@ -383,7 +382,9 @@ static int cow_create(const char *filename, QemuOpts *opts, Error **errp)
exit:
g_free(image_filename);
bdrv_unref(cow_bs);
if (cow_bs) {
bdrv_unref(cow_bs);
}
return ret;
}