* [PATCH AUTOSEL 5.7 05/28] bcache: check and adjust logical block size for backing devices [not found] <20200623173523.1355411-1-sashal@kernel.org> @ 2020-06-23 17:35 ` Sasha Levin 2020-06-23 17:35 ` Sasha Levin 0 siblings, 1 reply; 2+ messages in thread From: Sasha Levin @ 2020-06-23 17:35 UTC (permalink / raw) To: linux-kernel, stable Cc: Mauricio Faria de Oliveira, Ryan Finnie, Sebastian Marsching, Coly Li, Jens Axboe, Sasha Levin, linux-bcache From: Mauricio Faria de Oliveira <mfo@canonical.com> [ Upstream commit dcacbc1242c71e18fa9d2eadc5647e115c9c627d ] It's possible for a block driver to set logical block size to a value greater than page size incorrectly; e.g. bcache takes the value from the superblock, set by the user w/ make-bcache. This causes a BUG/NULL pointer dereference in the path: __blkdev_get() -> set_init_blocksize() // set i_blkbits based on ... -> bdev_logical_block_size() -> queue_logical_block_size() // ... this value -> bdev_disk_changed() ... -> blkdev_readpage() -> block_read_full_page() -> create_page_buffers() // size = 1 << i_blkbits -> create_empty_buffers() // give size/take pointer -> alloc_page_buffers() // return NULL .. BUG! Because alloc_page_buffers() is called with size > PAGE_SIZE, thus it initializes head = NULL, skips the loop, return head; then create_empty_buffers() gets (and uses) the NULL pointer. This has been around longer than commit ad6bf88a6c19 ("block: fix an integer overflow in logical block size"); however, it increased the range of values that can trigger the issue. Previously only 8k/16k/32k (on x86/4k page size) would do it, as greater values overflow unsigned short to zero, and queue_ logical_block_size() would then use the default of 512. Now the range with unsigned int is much larger, and users w/ the 512k value, which happened to be zero'ed previously and work fine, started to hit this issue -- as the zero is gone, and queue_logical_block_size() does return 512k (>PAGE_SIZE.) Fix this by checking the bcache device's logical block size, and if it's greater than page size, fallback to the backing/ cached device's logical page size. This doesn't affect cache devices as those are still checked for block/page size in read_super(); only the backing/cached devices are not. Apparently it's a regression from commit 2903381fce71 ("bcache: Take data offset from the bdev superblock."), moving the check into BCACHE_SB_VERSION_CDEV only. Now that we have superblocks of backing devices out there with this larger value, we cannot refuse to load them (i.e., have a similar check in _BDEV.) Ideally perhaps bcache should use all values from the backing device (physical/logical/io_min block size)? But for now just fix the problematic case. Test-case: # IMG=/root/disk.img # dd if=/dev/zero of=$IMG bs=1 count=0 seek=1G # DEV=$(losetup --find --show $IMG) # make-bcache --bdev $DEV --block 8k < see dmesg > Before: # uname -r 5.7.0-rc7 [ 55.944046] BUG: kernel NULL pointer dereference, address: 0000000000000000 ... [ 55.949742] CPU: 3 PID: 610 Comm: bcache-register Not tainted 5.7.0-rc7 #4 ... [ 55.952281] RIP: 0010:create_empty_buffers+0x1a/0x100 ... [ 55.966434] Call Trace: [ 55.967021] create_page_buffers+0x48/0x50 [ 55.967834] block_read_full_page+0x49/0x380 [ 55.972181] do_read_cache_page+0x494/0x610 [ 55.974780] read_part_sector+0x2d/0xaa [ 55.975558] read_lba+0x10e/0x1e0 [ 55.977904] efi_partition+0x120/0x5a6 [ 55.980227] blk_add_partitions+0x161/0x390 [ 55.982177] bdev_disk_changed+0x61/0xd0 [ 55.982961] __blkdev_get+0x350/0x490 [ 55.983715] __device_add_disk+0x318/0x480 [ 55.984539] bch_cached_dev_run+0xc5/0x270 [ 55.986010] register_bcache.cold+0x122/0x179 [ 55.987628] kernfs_fop_write+0xbc/0x1a0 [ 55.988416] vfs_write+0xb1/0x1a0 [ 55.989134] ksys_write+0x5a/0xd0 [ 55.989825] do_syscall_64+0x43/0x140 [ 55.990563] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 55.991519] RIP: 0033:0x7f7d60ba3154 ... After: # uname -r 5.7.0.bcachelbspgsz [ 31.672460] bcache: bcache_device_init() bcache0: sb/logical block size (8192) greater than page size (4096) falling back to device logical block size (512) [ 31.675133] bcache: register_bdev() registered backing device loop0 # grep ^ /sys/block/bcache0/queue/*_block_size /sys/block/bcache0/queue/logical_block_size:512 /sys/block/bcache0/queue/physical_block_size:8192 Reported-by: Ryan Finnie <ryan@finnie.org> Reported-by: Sebastian Marsching <sebastian@marsching.com> Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org> --- drivers/md/bcache/super.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index 4d8bf731b118c..a2e5a0fcd7d5c 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -819,7 +819,8 @@ static void bcache_device_free(struct bcache_device *d) } static int bcache_device_init(struct bcache_device *d, unsigned int block_size, - sector_t sectors, make_request_fn make_request_fn) + sector_t sectors, make_request_fn make_request_fn, + struct block_device *cached_bdev) { struct request_queue *q; const size_t max_stripes = min_t(size_t, INT_MAX, @@ -885,6 +886,21 @@ static int bcache_device_init(struct bcache_device *d, unsigned int block_size, q->limits.io_min = block_size; q->limits.logical_block_size = block_size; q->limits.physical_block_size = block_size; + + if (q->limits.logical_block_size > PAGE_SIZE && cached_bdev) { + /* + * This should only happen with BCACHE_SB_VERSION_BDEV. + * Block/page size is checked for BCACHE_SB_VERSION_CDEV. + */ + pr_info("%s: sb/logical block size (%u) greater than page size " + "(%lu) falling back to device logical block size (%u)", + d->disk->disk_name, q->limits.logical_block_size, + PAGE_SIZE, bdev_logical_block_size(cached_bdev)); + + /* This also adjusts physical block size/min io size if needed */ + blk_queue_logical_block_size(q, bdev_logical_block_size(cached_bdev)); + } + blk_queue_flag_set(QUEUE_FLAG_NONROT, d->disk->queue); blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, d->disk->queue); blk_queue_flag_set(QUEUE_FLAG_DISCARD, d->disk->queue); @@ -1342,7 +1358,7 @@ static int cached_dev_init(struct cached_dev *dc, unsigned int block_size) ret = bcache_device_init(&dc->disk, block_size, dc->bdev->bd_part->nr_sects - dc->sb.data_offset, - cached_dev_make_request); + cached_dev_make_request, dc->bdev); if (ret) return ret; @@ -1455,7 +1471,7 @@ static int flash_dev_run(struct cache_set *c, struct uuid_entry *u) kobject_init(&d->kobj, &bch_flash_dev_ktype); if (bcache_device_init(d, block_bytes(c), u->sectors, - flash_dev_make_request)) + flash_dev_make_request, NULL)) goto err; bcache_device_attach(d, c, u - c->uuids); -- 2.25.1 ^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH AUTOSEL 5.7 05/28] bcache: check and adjust logical block size for backing devices 2020-06-23 17:35 ` [PATCH AUTOSEL 5.7 05/28] bcache: check and adjust logical block size for backing devices Sasha Levin @ 2020-06-23 17:35 ` Sasha Levin 0 siblings, 0 replies; 2+ messages in thread From: Sasha Levin @ 2020-06-23 17:35 UTC (permalink / raw) To: linux-kernel, stable Cc: Mauricio Faria de Oliveira, Ryan Finnie, Sebastian Marsching, Coly Li, Jens Axboe, Sasha Levin, linux-bcache From: Mauricio Faria de Oliveira <mfo@canonical.com> [ Upstream commit dcacbc1242c71e18fa9d2eadc5647e115c9c627d ] It's possible for a block driver to set logical block size to a value greater than page size incorrectly; e.g. bcache takes the value from the superblock, set by the user w/ make-bcache. This causes a BUG/NULL pointer dereference in the path: __blkdev_get() -> set_init_blocksize() // set i_blkbits based on ... -> bdev_logical_block_size() -> queue_logical_block_size() // ... this value -> bdev_disk_changed() ... -> blkdev_readpage() -> block_read_full_page() -> create_page_buffers() // size = 1 << i_blkbits -> create_empty_buffers() // give size/take pointer -> alloc_page_buffers() // return NULL .. BUG! Because alloc_page_buffers() is called with size > PAGE_SIZE, thus it initializes head = NULL, skips the loop, return head; then create_empty_buffers() gets (and uses) the NULL pointer. This has been around longer than commit ad6bf88a6c19 ("block: fix an integer overflow in logical block size"); however, it increased the range of values that can trigger the issue. Previously only 8k/16k/32k (on x86/4k page size) would do it, as greater values overflow unsigned short to zero, and queue_ logical_block_size() would then use the default of 512. Now the range with unsigned int is much larger, and users w/ the 512k value, which happened to be zero'ed previously and work fine, started to hit this issue -- as the zero is gone, and queue_logical_block_size() does return 512k (>PAGE_SIZE.) Fix this by checking the bcache device's logical block size, and if it's greater than page size, fallback to the backing/ cached device's logical page size. This doesn't affect cache devices as those are still checked for block/page size in read_super(); only the backing/cached devices are not. Apparently it's a regression from commit 2903381fce71 ("bcache: Take data offset from the bdev superblock."), moving the check into BCACHE_SB_VERSION_CDEV only. Now that we have superblocks of backing devices out there with this larger value, we cannot refuse to load them (i.e., have a similar check in _BDEV.) Ideally perhaps bcache should use all values from the backing device (physical/logical/io_min block size)? But for now just fix the problematic case. Test-case: # IMG=/root/disk.img # dd if=/dev/zero of=$IMG bs=1 count=0 seek=1G # DEV=$(losetup --find --show $IMG) # make-bcache --bdev $DEV --block 8k < see dmesg > Before: # uname -r 5.7.0-rc7 [ 55.944046] BUG: kernel NULL pointer dereference, address: 0000000000000000 ... [ 55.949742] CPU: 3 PID: 610 Comm: bcache-register Not tainted 5.7.0-rc7 #4 ... [ 55.952281] RIP: 0010:create_empty_buffers+0x1a/0x100 ... [ 55.966434] Call Trace: [ 55.967021] create_page_buffers+0x48/0x50 [ 55.967834] block_read_full_page+0x49/0x380 [ 55.972181] do_read_cache_page+0x494/0x610 [ 55.974780] read_part_sector+0x2d/0xaa [ 55.975558] read_lba+0x10e/0x1e0 [ 55.977904] efi_partition+0x120/0x5a6 [ 55.980227] blk_add_partitions+0x161/0x390 [ 55.982177] bdev_disk_changed+0x61/0xd0 [ 55.982961] __blkdev_get+0x350/0x490 [ 55.983715] __device_add_disk+0x318/0x480 [ 55.984539] bch_cached_dev_run+0xc5/0x270 [ 55.986010] register_bcache.cold+0x122/0x179 [ 55.987628] kernfs_fop_write+0xbc/0x1a0 [ 55.988416] vfs_write+0xb1/0x1a0 [ 55.989134] ksys_write+0x5a/0xd0 [ 55.989825] do_syscall_64+0x43/0x140 [ 55.990563] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 55.991519] RIP: 0033:0x7f7d60ba3154 ... After: # uname -r 5.7.0.bcachelbspgsz [ 31.672460] bcache: bcache_device_init() bcache0: sb/logical block size (8192) greater than page size (4096) falling back to device logical block size (512) [ 31.675133] bcache: register_bdev() registered backing device loop0 # grep ^ /sys/block/bcache0/queue/*_block_size /sys/block/bcache0/queue/logical_block_size:512 /sys/block/bcache0/queue/physical_block_size:8192 Reported-by: Ryan Finnie <ryan@finnie.org> Reported-by: Sebastian Marsching <sebastian@marsching.com> Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org> --- drivers/md/bcache/super.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index 4d8bf731b118c..a2e5a0fcd7d5c 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -819,7 +819,8 @@ static void bcache_device_free(struct bcache_device *d) } static int bcache_device_init(struct bcache_device *d, unsigned int block_size, - sector_t sectors, make_request_fn make_request_fn) + sector_t sectors, make_request_fn make_request_fn, + struct block_device *cached_bdev) { struct request_queue *q; const size_t max_stripes = min_t(size_t, INT_MAX, @@ -885,6 +886,21 @@ static int bcache_device_init(struct bcache_device *d, unsigned int block_size, q->limits.io_min = block_size; q->limits.logical_block_size = block_size; q->limits.physical_block_size = block_size; + + if (q->limits.logical_block_size > PAGE_SIZE && cached_bdev) { + /* + * This should only happen with BCACHE_SB_VERSION_BDEV. + * Block/page size is checked for BCACHE_SB_VERSION_CDEV. + */ + pr_info("%s: sb/logical block size (%u) greater than page size " + "(%lu) falling back to device logical block size (%u)", + d->disk->disk_name, q->limits.logical_block_size, + PAGE_SIZE, bdev_logical_block_size(cached_bdev)); + + /* This also adjusts physical block size/min io size if needed */ + blk_queue_logical_block_size(q, bdev_logical_block_size(cached_bdev)); + } + blk_queue_flag_set(QUEUE_FLAG_NONROT, d->disk->queue); blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, d->disk->queue); blk_queue_flag_set(QUEUE_FLAG_DISCARD, d->disk->queue); @@ -1342,7 +1358,7 @@ static int cached_dev_init(struct cached_dev *dc, unsigned int block_size) ret = bcache_device_init(&dc->disk, block_size, dc->bdev->bd_part->nr_sects - dc->sb.data_offset, - cached_dev_make_request); + cached_dev_make_request, dc->bdev); if (ret) return ret; @@ -1455,7 +1471,7 @@ static int flash_dev_run(struct cache_set *c, struct uuid_entry *u) kobject_init(&d->kobj, &bch_flash_dev_ktype); if (bcache_device_init(d, block_bytes(c), u->sectors, - flash_dev_make_request)) + flash_dev_make_request, NULL)) goto err; bcache_device_attach(d, c, u - c->uuids); -- 2.25.1 ^ permalink raw reply related [flat|nested] 2+ messages in thread
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2020-06-23 17:35 ` [PATCH AUTOSEL 5.7 05/28] bcache: check and adjust logical block size for backing devices Sasha Levin
2020-06-23 17:35 ` Sasha Levin
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