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Re: [Qemu-devel] [PATCH] block: fix null-pointer bug on error case in bl
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH] block: fix null-pointer bug on error case in block commit |
Date: |
Wed, 16 Jan 2013 12:54:20 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) |
Jeff Cody <address@hidden> writes:
> This is a bug that was caught by a coverity run by Markus. In
> the error case when we errored out to exit_restore_open early in the
> function, 'overlay_bs' was still NULL at that point, although it is
> used to look up flags and perform a bdrv_reopen().
>
> Move the overlay_bs lookup to where it is needed, and check for NULL
> before restoring the flags. Also get rid of the unneeded parameter
> initialization.
>
> Reported-By: Markus Armbruster <address@hidden>
> Signed-off-by: Jeff Cody <address@hidden>
> ---
> block/commit.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/block/commit.c b/block/commit.c
> index 61ebdba..553447e 100644
> --- a/block/commit.c
> +++ b/block/commit.c
> @@ -65,7 +65,7 @@ static void coroutine_fn commit_run(void *opaque)
> BlockDriverState *active = s->active;
> BlockDriverState *top = s->top;
> BlockDriverState *base = s->base;
> - BlockDriverState *overlay_bs = NULL;
> + BlockDriverState *overlay_bs;
> int64_t sector_num, end;
> int ret = 0;
> int n = 0;
> @@ -92,8 +92,6 @@ static void coroutine_fn commit_run(void *opaque)
> }
> }
>
> - overlay_bs = bdrv_find_overlay(active, top);
> -
> end = s->common.len >> BDRV_SECTOR_BITS;
> buf = qemu_blockalign(top, COMMIT_BUFFER_SIZE);
>
> @@ -156,7 +154,8 @@ exit_restore_reopen:
> if (s->base_flags != bdrv_get_flags(base)) {
> bdrv_reopen(base, s->base_flags, NULL);
> }
> - if (s->orig_overlay_flags != bdrv_get_flags(overlay_bs)) {
> + overlay_bs = bdrv_find_overlay(active, top);
> + if (overlay_bs && s->orig_overlay_flags != bdrv_get_flags(overlay_bs)) {
> bdrv_reopen(overlay_bs, s->orig_overlay_flags, NULL);
> }
The move doesn't change anything in the "no error" case, because we
don't change active, top or the BDS chain connecting them between old
and new location.
Reviewed-by: Markus Armbruster <address@hidden>