From be360c83f2d810493c04f999d69ec9152981e0c0 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Sun, 22 Jan 2023 14:02:57 -0500 Subject: dm flakey: don't corrupt the zero page commit f50714b57aecb6b3dc81d578e295f86d9c73f078 upstream. 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 Reviewed-by: Sweet Tea Dorminy Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-flakey.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'drivers/md') diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c index 220bbf354bb0..805a70abe437 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", -- cgit v1.2.3