| Message ID | 20241203174643.1259197-1-mtsai@redhat.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Delegated to: | Mike Snitzer |
| Headers | show |
| Series | [1/3] dm array: fix releasing a faulty array block twice in dm_array_cursor_end | expand |
Reviewed-by: thornber@redhat.com On Tue, Dec 3, 2024 at 5:47 PM Ming-Hung Tsai <mtsai@redhat.com> wrote: > > When dm_bm_read_lock() fails due to locking or checksum errors, it > releases the faulty block implicitly while leaving an invalid output > pointer behind. The caller of dm_bm_read_lock() should not operate on > this invalid dm_block pointer, or it will lead to undefined result. > For example, the dm_array_cursor incorrectly caches the invalid pointer > on reading a faulty array block, causing a double release in > dm_array_cursor_end(), then hitting the BUG_ON in dm-bufio cache_put(). > > Reproduce steps: > > 1. initialize a cache device > > 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 $262144" > dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 > dmsetup create cache --table "0 524288 cache /dev/mapper/cmeta \ > /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" > > 2. wipe the second array block offline > > dmsteup remove cache cmeta cdata corig > mapping_root=$(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 reopen the cache device > > 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 --table "0 524288 cache /dev/mapper/cmeta \ > /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" > > Kernel logs: > > (snip) > device-mapper: array: array_block_check failed: blocknr 0 != wanted 10 > device-mapper: block manager: array validator check failed for block 10 > device-mapper: array: get_ablock failed > device-mapper: cache metadata: dm_array_cursor_next for mapping failed > ------------[ cut here ]------------ > kernel BUG at drivers/md/dm-bufio.c:638! > > Fix by setting the cached block pointer to NULL on errors. > > Signed-off-by: Ming-Hung Tsai <mtsai@redhat.com> > Fixes: fdd1315aa5f0 ("dm array: introduce cursor api") > --- > drivers/md/persistent-data/dm-array.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/md/persistent-data/dm-array.c b/drivers/md/persistent-data/dm-array.c > index 157c9bd2fed7..c46a374f7459 100644 > --- a/drivers/md/persistent-data/dm-array.c > +++ b/drivers/md/persistent-data/dm-array.c > @@ -917,23 +917,28 @@ static int load_ablock(struct dm_array_cursor *c) > if (c->block) > unlock_ablock(c->info, c->block); > > - c->block = NULL; > - c->ab = NULL; > c->index = 0; > > r = dm_btree_cursor_get_value(&c->cursor, &key, &value_le); > if (r) { > DMERR("dm_btree_cursor_get_value failed"); > dm_btree_cursor_end(&c->cursor); > + goto out; > > } else { > r = get_ablock(c->info, le64_to_cpu(value_le), &c->block, &c->ab); > if (r) { > DMERR("get_ablock failed"); > dm_btree_cursor_end(&c->cursor); > + goto out; > } > } > > + return 0; > + > +out: > + c->block = NULL; > + c->ab = NULL; > return r; > } > > -- > 2.47.0 >
diff --git a/drivers/md/persistent-data/dm-array.c b/drivers/md/persistent-data/dm-array.c index 157c9bd2fed7..c46a374f7459 100644 --- a/drivers/md/persistent-data/dm-array.c +++ b/drivers/md/persistent-data/dm-array.c @@ -917,23 +917,28 @@ static int load_ablock(struct dm_array_cursor *c) if (c->block) unlock_ablock(c->info, c->block); - c->block = NULL; - c->ab = NULL; c->index = 0; r = dm_btree_cursor_get_value(&c->cursor, &key, &value_le); if (r) { DMERR("dm_btree_cursor_get_value failed"); dm_btree_cursor_end(&c->cursor); + goto out; } else { r = get_ablock(c->info, le64_to_cpu(value_le), &c->block, &c->ab); if (r) { DMERR("get_ablock failed"); dm_btree_cursor_end(&c->cursor); + goto out; } } + return 0; + +out: + c->block = NULL; + c->ab = NULL; return r; }
When dm_bm_read_lock() fails due to locking or checksum errors, it releases the faulty block implicitly while leaving an invalid output pointer behind. The caller of dm_bm_read_lock() should not operate on this invalid dm_block pointer, or it will lead to undefined result. For example, the dm_array_cursor incorrectly caches the invalid pointer on reading a faulty array block, causing a double release in dm_array_cursor_end(), then hitting the BUG_ON in dm-bufio cache_put(). Reproduce steps: 1. initialize a cache device 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 $262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 dmsetup create cache --table "0 524288 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" 2. wipe the second array block offline dmsteup remove cache cmeta cdata corig mapping_root=$(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 reopen the cache device 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 --table "0 524288 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" Kernel logs: (snip) device-mapper: array: array_block_check failed: blocknr 0 != wanted 10 device-mapper: block manager: array validator check failed for block 10 device-mapper: array: get_ablock failed device-mapper: cache metadata: dm_array_cursor_next for mapping failed ------------[ cut here ]------------ kernel BUG at drivers/md/dm-bufio.c:638! Fix by setting the cached block pointer to NULL on errors. Signed-off-by: Ming-Hung Tsai <mtsai@redhat.com> Fixes: fdd1315aa5f0 ("dm array: introduce cursor api") --- drivers/md/persistent-data/dm-array.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)