kernel/linux.git/drivers/md/dm-cache-target.c, branch v6.6.141

dm cache: fix missing return in invalidate_committed's error path

2026-05-23T11:03:15+00:00

[ Upstream commit 8c0ee19db81f0fa1ff25fd75b22b17c0cc2acde3 ] In passthrough mode, dm-cache defers write submission until after metadata commit completes via the invalidate_committed() continuation. On commit error, invalidate_committed() calls invalidate_complete() to end the bio and free the migration struct, after which it should return immediately. The patch 4ca8b8bd952d ("dm cache: fix write hang in passthrough mode") omitted this early return, causing execution to fall through into the success path on error. This results in use-after-free on the migration struct in the subsequent calls. Fix by adding the missing return after the invalidate_complete() call. Fixes: 4ca8b8bd952d ("dm cache: fix write hang in passthrough mode") Reported-by: Dan Carpenter Closes: https://lore.kernel.org/dm-devel/adjMq6T5RRjv_uxM@stanley.mountain/ Signed-off-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka Signed-off-by: Sasha Levin

dm cache: fix dirty mapping checking in passthrough mode switching

2026-05-23T11:03:10+00:00

[ Upstream commit 322586745bd1a0e5f3559fd1635fdeb4dbd1d6b8 ] As mentioned in commit 9b1cc9f251af ("dm cache: share cache-metadata object across inactive and active DM tables"), dm-cache assumed table reload occurs after suspension, while LVM's table preload breaks this assumption. The dirty mapping check for passthrough mode was designed around this assumption and is performed during table creation, causing the check to fail with preload while metadata updates are ongoing. This risks loading dirty mappings into passthrough mode, resulting in data loss. Reproduce steps: 1. Create a writeback cache with zero migration_threshold to produce dirty mappings dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 131072 linear /dev/sdc 8192" dmsetup create corig --table "0 262144 linear /dev/sdc 262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writeback smq \ 2 migration_threshold 0" 2. Preload a table in passthrough mode dmsetup reload cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 passthrough smq 0" 3. Write to the first cache block to make it dirty fio --filename=/dev/mapper/cache --name=populate --rw=write --bs=4k \ --direct=1 --size=64k 4. Resume the inactive table. Now it's possible to load the dirty block into passthrough mode. dmsetup resume cache Fix by moving the checks to the preresume phase to support table preloading. Also remove the unused function dm_cache_metadata_all_clean. Fixes: 2ee57d587357 ("dm cache: add passthrough mode") Signed-off-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka Signed-off-by: Sasha Levin

dm cache: support shrinking the origin device

2026-05-23T11:03:10+00:00

[ Upstream commit c2662b1544cbd8ea3181381bb899b8e681dfedc7 ] This patch introduces formal support for shrinking the cache origin by reducing the cache target length via table reloads. Cache blocks mapped beyond the new target length must be clean and are invalidated during preresume. If any dirty blocks exist in the area being removed, the preresume operation fails without setting the NEEDS_CHECK flag in superblock, and the resume ioctl returns EFBIG. The cache device remains suspended until a table reload with target length that fits existing mappings is performed. Without this patch, reducing the cache target length could result in io errors (RHBZ: 2134334), out-of-bounds memory access to the discard bitset, and security concerns regarding data leakage. Verification steps: 1. create a cache metadata with some cached blocks mapped to the tail of the origin device. Here we use cache_restore v1.0 to build a metadata with one clean block mapped to the last origin block. cat <> cmeta.xml EOF dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" cache_restore -i cmeta.xml -o /dev/mapper/cmeta --metadata-version=2 dmsetup remove cmeta 2. bring up the cache whilst shrinking the cache origin by one block: dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 65536 linear /dev/sdc 8192" dmsetup create corig --table "0 524160 linear /dev/sdc 262144" dmsetup create cache --table "0 524160 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" 3. check the number of cached data blocks via dmsetup status. It is expected to be zero. dmsetup status cache | cut -d ' ' -f 7 In addition to the script above, this patch can be verified using the "cache/resize" tests in dmtest-python: ./dmtest run --rx cache/resize/shrink_origin --result-set default Signed-off-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka Stable-dep-of: 322586745bd1 ("dm cache: fix dirty mapping checking in passthrough mode switching") Signed-off-by: Sasha Levin

dm cache: fix concurrent write failure in passthrough mode

2026-05-23T11:03:10+00:00

[ Upstream commit e4f66341779d0cf4c83c74793753a84094286d9e ] When bio prison cell lock acquisition fails due to concurrent writes to the same block in passthrough mode, dm-cache incorrectly returns an I/O error instead of properly handling the concurrency. This can occur in both process and workqueue contexts when invalidate_lock() is called for exclusive access to a data block. Fix this by deferring the write bios to ensure proper block device behavior. Reproduce steps: 1. Create a cache device dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 131072 linear /dev/sdc 8192" dmsetup create corig --table "0 262144 linear /dev/sdc 262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" 2. Promote the first data block into cache fio --filename=/dev/mapper/cache --name=populate --rw=write --bs=4k \ --direct=1 --size=64k 3. Reload the cache into passthrough mode dmsetup suspend cache dmsetup reload cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 passthrough smq 0" dmsetup resume cache 4. Write to the first cached block concurrently. Sometimes one of the processes will receive I/O errors. fio --filename=/dev/mapper/cache --name test --rw=randwrite --bs=4k \ --randrepeat=0 --direct=1 --numjobs=2 --size 64k fio-3.41 fio: io_u error on file /dev/mapper/cache: Input/output error: write offset=4096, buflen=4096 fio: pid=106, err=5/file:io_u.c:2008, func=io_u error, error=Input/output error test: (groupid=0, jobs=1): err= 0: pid=105 test: (groupid=0, jobs=1): err= 5 (file:io_u.c:2008, func=io_u error, error=Input/output error): pid=106 Fixes: b29d4986d0da ("dm cache: significant rework to leverage dm-bio-prison-v2") Signed-off-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka Signed-off-by: Sasha Levin

dm cache: fix write hang in passthrough mode

2026-05-23T11:03:10+00:00

[ Upstream commit 4ca8b8bd952df7c3ccdc68af9bd3419d0839a04b ] The invalidate_remove() function has incomplete logic for handling write hit bios after cache invalidation. It sets up the remapping for the overwrite_bio but then drops it immediately without submission, causing write operations to hang. Fix by adding a new invalidate_committed() continuation that submits the remapped writes to the cache origin after metadata commit completes, while using the overwrite_endio hook to ensure proper completion sequencing. This maintains existing coherency. Also improve error handling in invalidate_complete() to preserve the original error status instead of using bio_io_error() unconditionally. Fixes: b29d4986d0da ("dm cache: significant rework to leverage dm-bio-prison-v2") Signed-off-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka Signed-off-by: Sasha Levin

dm cache: fix write path cache coherency in passthrough mode

2026-05-23T11:03:10+00:00

[ Upstream commit 0c5eef0aad508231d8e43ff8392692925e131b68 ] In passthrough mode, dm-cache defers write bio submission until cache invalidation completes to maintain existing coherency, requiring the target map function to return DM_MAPIO_SUBMITTED. The current map_bio() returns DM_MAPIO_REMAPPED, violating the required ordering constraint. Reproduce steps: 1. Create a cache device dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 131072 linear /dev/sdc 8192" dmsetup create corig --table "0 262144 linear /dev/sdc 262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" 2. Promote the first data block into the cache fio --filename=/dev/mapper/cache --name=populate --rw=write --bs=4k \ --direct=1 --size=64k 3. Reload the cache into passthrough mode dmsetup suspend cache dmsetup reload cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 passthrough smq 0" dmsetup resume cache 4. Write to the first data block, and check io ordering using ftrace echo 1 > /sys/kernel/debug/tracing/events/block/block_bio_queue/enable echo 1 > /sys/kernel/debug/tracing/events/block/block_bio_complete/enable echo 1 > /sys/kernel/debug/tracing/events/block/block_rq_complete/enable fio --filename=/dev/mapper/cache --name=test --rw=write --bs=64k \ --direct=1 --size 64k 5. ftrace logs show that write operations to the cache origin (252:2) and metadata operations (252:0) are unsynchronized: the origin write occurs before metadata commit. fio-146 [000] ..... 420.139562: block_bio_queue: 252,3 WS 0 + 128 [fio] fio-146 [000] ..... 420.149395: block_bio_queue: 252,2 WS 0 + 128 [fio] fio-146 [000] ..... 420.149763: block_bio_queue: 8,32 WS 262144 + 128 [fio] fio-146 [000] dNh1. 420.151446: block_rq_complete: 8,32 WS () 262144 + 128 be,0,4 [0] fio-146 [000] dNh1. 420.152731: block_bio_complete: 252,2 WS 0 + 128 [0] fio-146 [000] dNh1. 420.154229: block_bio_complete: 252,3 WS 0 + 128 [0] kworker/0:0-9 [000] ..... 420.160530: block_bio_queue: 252,0 W 408 + 8 [kworker/0:0] kworker/0:0-9 [000] ..... 420.161641: block_bio_queue: 8,32 W 408 + 8 [kworker/0:0] kworker/0:0-9 [000] ..... 420.162533: block_bio_queue: 252,0 W 416 + 8 [kworker/0:0] kworker/0:0-9 [000] ..... 420.162821: block_bio_queue: 8,32 W 416 + 8 [kworker/0:0] Fixes: b29d4986d0da ("dm cache: significant rework to leverage dm-bio-prison-v2") Signed-off-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka Signed-off-by: Sasha Levin

dm cache: fix null-deref with concurrent writes in passthrough mode

2026-05-23T11:03:10+00:00

[ Upstream commit 7d1f98d668ee34c1d15bdc0420fdd062f24a27c0 ] In passthrough mode, when dm-cache starts to invalidate a cache entry and bio prison cell lock fails due to concurrent write to the same cached block, mg->cell remains NULL. The error path in invalidate_complete() attempts to unlock and free the cell unconditionally, causing a NULL pointer dereference: KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 0 UID: 0 PID: 134 Comm: fio Not tainted 6.19.0-rc7 #3 PREEMPT RIP: 0010:dm_cell_unlock_v2+0x3f/0x210 Call Trace: invalidate_complete+0xef/0x430 map_bio+0x130f/0x1a10 cache_map+0x320/0x6b0 __map_bio+0x458/0x510 dm_submit_bio+0x40e/0x16d0 __submit_bio+0x419/0x870 Reproduce steps: 1. Create a cache device dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 131072 linear /dev/sdc 8192" dmsetup create corig --table "0 262144 linear /dev/sdc 262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" 2. Promote the first data block into cache fio --filename=/dev/mapper/cache --name=populate --rw=write --bs=4k \ --direct=1 --size=64k 3. Reload the cache into passthrough mode dmsetup suspend cache dmsetup reload cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 passthrough smq 0" dmsetup resume cache 4. Write to the first cached block concurrently fio --filename=/dev/mapper/cache --name test --rw=randwrite --bs=4k \ --randrepeat=0 --direct=1 --numjobs=2 --size 64k Fix by checking if mg->cell is valid before attempting to unlock it. Fixes: b29d4986d0da ("dm cache: significant rework to leverage dm-bio-prison-v2") Signed-off-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka Signed-off-by: Sasha Levin

dm cache: prevent BUG_ON by blocking retries on failed device resumes

2025-06-04T12:42:02+00:00

[ Upstream commit 5da692e2262b8f81993baa9592f57d12c2703dea ] A cache device failing to resume due to mapping errors should not be retried, as the failure leaves a partially initialized policy object. Repeating the resume operation risks triggering BUG_ON when reloading cache mappings into the incomplete policy object. Reproduce steps: 1. create a cache metadata consisting of 512 or more cache blocks, with some mappings stored in the first array block of the mapping array. Here we use cache_restore v1.0 to build the metadata. cat <> cmeta.xml EOF dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" cache_restore -i cmeta.xml -o /dev/mapper/cmeta --metadata-version=2 dmsetup remove cmeta 2. wipe the second array block of the mapping array to simulate data degradations. mapping_root=$(dd if=/dev/sdc bs=1c count=8 skip=192 \ 2>/dev/null | hexdump -e '1/8 "%u\n"') ablock=$(dd if=/dev/sdc bs=1c count=8 skip=$((4096*mapping_root+2056)) \ 2>/dev/null | hexdump -e '1/8 "%u\n"') dd if=/dev/zero of=/dev/sdc bs=4k count=1 seek=$ablock 3. try bringing up the cache device. The resume is expected to fail due to the broken array block. dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 65536 linear /dev/sdc 8192" dmsetup create corig --table "0 524288 linear /dev/sdc 262144" dmsetup create cache --notable dmsetup load cache --table "0 524288 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" dmsetup resume cache 4. try resuming the cache again. An unexpected BUG_ON is triggered while loading cache mappings. dmsetup resume cache Kernel logs: (snip) ------------[ cut here ]------------ kernel BUG at drivers/md/dm-cache-policy-smq.c:752! Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI CPU: 0 UID: 0 PID: 332 Comm: dmsetup Not tainted 6.13.4 #3 RIP: 0010:smq_load_mapping+0x3e5/0x570 Fix by disallowing resume operations for devices that failed the initial attempt. Signed-off-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka Signed-off-by: Sasha Levin

dm-cache: fix warnings about duplicate slab caches

2024-12-09T09:32:40+00:00

commit 346dbf1b1345476a6524512892cceb931bee3039 upstream. The commit 4c39529663b9 adds a warning about duplicate cache names if CONFIG_DEBUG_VM is selected. These warnings are triggered by the dm-cache code. The dm-cache code allocates a slab cache for each device. This commit changes it to allocate just one slab cache in the module init function. Signed-off-by: Mikulas Patocka Fixes: 4c39529663b9 ("slab: Warn on duplicate cache names when DEBUG_VM=y") Signed-off-by: Greg Kroah-Hartman

dm cache: fix potential out-of-bounds access on the first resume

2024-11-14T12:19:37+00:00

commit c0ade5d98979585d4f5a93e4514c2e9a65afa08d upstream. Out-of-bounds access occurs if the fast device is expanded unexpectedly before the first-time resume of the cache table. This happens because expanding the fast device requires reloading the cache table for cache_create to allocate new in-core data structures that fit the new size, and the check in cache_preresume is not performed during the first resume, leading to the issue. Reproduce steps: 1. prepare component devices: dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 65536 linear /dev/sdc 8192" dmsetup create corig --table "0 524288 linear /dev/sdc 262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct 2. load a cache table of 512 cache blocks, and deliberately expand the fast device before resuming the cache, making the in-core data structures inadequate. dmsetup create cache --notable dmsetup reload cache --table "0 524288 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" dmsetup reload cdata --table "0 131072 linear /dev/sdc 8192" dmsetup resume cdata dmsetup resume cache 3. suspend the cache to write out the in-core dirty bitset and hint array, leading to out-of-bounds access to the dirty bitset at offset 0x40: dmsetup suspend cache KASAN reports: BUG: KASAN: vmalloc-out-of-bounds in is_dirty_callback+0x2b/0x80 Read of size 8 at addr ffffc90000085040 by task dmsetup/90 (...snip...) The buggy address belongs to the virtual mapping at [ffffc90000085000, ffffc90000087000) created by: cache_ctr+0x176a/0x35f0 (...snip...) Memory state around the buggy address: ffffc90000084f00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ffffc90000084f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 >ffffc90000085000: 00 00 00 00 00 00 00 00 f8 f8 f8 f8 f8 f8 f8 f8 ^ ffffc90000085080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ffffc90000085100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 Fix by checking the size change on the first resume. Signed-off-by: Ming-Hung Tsai Fixes: f494a9c6b1b6 ("dm cache: cache shrinking support") Cc: stable@vger.kernel.org Signed-off-by: Mikulas Patocka Acked-by: Joe Thornber Signed-off-by: Greg Kroah-Hartman