The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.14.y git checkout FETCH_HEAD git cherry-pick -x f50714b57aecb6b3dc81d578e295f86d9c73f078 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '167819221463150@kroah.com' --subject-prefix 'PATCH 4.14.y' HEAD^..

Possible dependencies:

f50714b57aec ("dm flakey: don't corrupt the zero page") a00f5276e266 ("dm flakey: Properly corrupt multi-page bios.")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f50714b57aecb6b3dc81d578e295f86d9c73f078 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka mpatocka@redhat.com Date: Sun, 22 Jan 2023 14:02:57 -0500 Subject: [PATCH] dm flakey: don't corrupt the zero page

When we need to zero some range on a block device, the function __blkdev_issue_zero_pages submits a write bio with the bio vector pointing to the zero page. If we use dm-flakey with corrupt bio writes option, it will corrupt the content of the zero page which results in crashes of various userspace programs. Glibc assumes that memory returned by mmap is zeroed and it uses it for calloc implementation; if the newly mapped memory is not zeroed, calloc will return non-zeroed memory.

Fix this bug by testing if the page is equal to ZERO_PAGE(0) and avoiding the corruption in this case.

Cc: stable@vger.kernel.org Fixes: a00f5276e266 ("dm flakey: Properly corrupt multi-page bios.") Signed-off-by: Mikulas Patocka mpatocka@redhat.com Reviewed-by: Sweet Tea Dorminy sweettea-kernel@dorminy.me Signed-off-by: Mike Snitzer snitzer@kernel.org

diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c index 89fa7a68c6c4..ff9ca5b2a47e 100644 --- a/drivers/md/dm-flakey.c +++ b/drivers/md/dm-flakey.c @@ -303,8 +303,11 @@ static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc) */ bio_for_each_segment(bvec, bio, iter) { if (bio_iter_len(bio, iter) > corrupt_bio_byte) { - char *segment = (page_address(bio_iter_page(bio, iter)) - + bio_iter_offset(bio, iter)); + char *segment; + struct page *page = bio_iter_page(bio, iter); + if (unlikely(page == ZERO_PAGE(0))) + break; + segment = (page_address(page) + bio_iter_offset(bio, iter)); segment[corrupt_bio_byte] = fc->corrupt_bio_value; DMDEBUG("Corrupting data bio=%p by writing %u to byte %u " "(rw=%c bi_opf=%u bi_sector=%llu size=%u)\n",