Re: [PATCH] block: Replace bio_check_ro()'s WARN_ON()

Kees Cook
2019-11-22T18:53:28Z

Friendly ping! I keep tripping over this. Can this please get applied so
we can silence syzbot and avoid needless WARNs? :)

-Kees

On Fri, Aug 24, 2018 at 02:15:35PM -0700, Kees Cook wrote:
> As described in commit 96c6a32ccb55a ("include/asm-generic/bug.h: clarify
> valid uses of WARN()"), this replaces a userspace-reachable WARN_ON()
> with pr_warn_once(). The reachability is even noted in the existing
> comment. This appears to be an "expected by unlikely" condition, so
> getting rid of the WARN_ON() means kernel fuzzers will stop reporting
> the problem. Additionally un-breaks the error string so it can more
> easily be found with grep.
>
> Reported-by: syzbot+21cfe1f803e0e158acf1@syzkaller.appspotmail.com
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: linux-block@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> block/blk-core.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index dee56c282efb..470c3cea8cb0 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -2166,11 +2166,9 @@ static inline bool bio_check_ro(struct bio *bio, struct hd_struct *part)
> if (part->policy && (op_is_write(op) && !op_is_flush(op))) {
> char b[BDEVNAME_SIZE];
>
> - WARN_ONCE(1,
> - "generic_make_request: Trying to write "
> - "to read-only block-device %s (partno %d)\n",
> + /* Older lvm-tools actually triggers this. */
> + pr_warn_once("Trying to write to read-only block-device %s (partno %d)\n",
> bio_devname(bio, b), part->partno);
> - /* Older lvm-tools actually trigger this */
> return false;
> }
>
> --
> 2.17.1
>
>
> --
> Kees Cook
> Pixel Security

--
Kees Cook