6.6-stable review patch. If anyone has any objections, please let me know.
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From: Qu Wenruo wqu@suse.com
commit f546c4282673497a06ecb6190b50ae7f6c85b02f upstream.
[BUG] There is a bug report that, on a ext4-converted btrfs, scrub leads to various problems, including:
- "unable to find chunk map" errors BTRFS info (device vdb): scrub: started on devid 1 BTRFS critical (device vdb): unable to find chunk map for logical 2214744064 length 4096 BTRFS critical (device vdb): unable to find chunk map for logical 2214744064 length 45056
This would lead to unrepariable errors.
- Use-after-free KASAN reports: ================================================================== BUG: KASAN: slab-use-after-free in __blk_rq_map_sg+0x18f/0x7c0 Read of size 8 at addr ffff8881013c9040 by task btrfs/909 CPU: 0 PID: 909 Comm: btrfs Not tainted 6.7.0-x64v3-dbg #11 c50636e9419a8354555555245df535e380563b2b Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 2023.11-2 12/24/2023 Call Trace: <TASK> dump_stack_lvl+0x43/0x60 print_report+0xcf/0x640 kasan_report+0xa6/0xd0 __blk_rq_map_sg+0x18f/0x7c0 virtblk_prep_rq.isra.0+0x215/0x6a0 [virtio_blk 19a65eeee9ae6fcf02edfad39bb9ddee07dcdaff] virtio_queue_rqs+0xc4/0x310 [virtio_blk 19a65eeee9ae6fcf02edfad39bb9ddee07dcdaff] blk_mq_flush_plug_list.part.0+0x780/0x860 __blk_flush_plug+0x1ba/0x220 blk_finish_plug+0x3b/0x60 submit_initial_group_read+0x10a/0x290 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] flush_scrub_stripes+0x38e/0x430 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] scrub_stripe+0x82a/0xae0 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] scrub_chunk+0x178/0x200 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] scrub_enumerate_chunks+0x4bc/0xa30 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] btrfs_scrub_dev+0x398/0x810 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] btrfs_ioctl+0x4b9/0x3020 [btrfs e57987a360bed82fe8756dcd3e0de5406ccfe965] __x64_sys_ioctl+0xbd/0x100 do_syscall_64+0x5d/0xe0 entry_SYSCALL_64_after_hwframe+0x63/0x6b RIP: 0033:0x7f47e5e0952b
- Crash, mostly due to above use-after-free
[CAUSE] The converted fs has the following data chunk layout:
item 2 key (FIRST_CHUNK_TREE CHUNK_ITEM 2214658048) itemoff 16025 itemsize 80 length 86016 owner 2 stripe_len 65536 type DATA|single
For above logical bytenr 2214744064, it's at the chunk end (2214658048 + 86016 = 2214744064).
This means btrfs_submit_bio() would split the bio, and trigger endio function for both of the two halves.
However scrub_submit_initial_read() would only expect the endio function to be called once, not any more. This means the first endio function would already free the bbio::bio, leaving the bvec freed, thus the 2nd endio call would lead to use-after-free.
[FIX] - Make sure scrub_read_endio() only updates bits in its range Since we may read less than 64K at the end of the chunk, we should not touch the bits beyond chunk boundary.
- Make sure scrub_submit_initial_read() only to read the chunk range This is done by calculating the real number of sectors we need to read, and add sector-by-sector to the bio.
Thankfully the scrub read repair path won't need extra fixes:
- scrub_stripe_submit_repair_read() With above fixes, we won't update error bit for range beyond chunk, thus scrub_stripe_submit_repair_read() should never submit any read beyond the chunk.
Reported-by: Rongrong i@rong.moe Fixes: e02ee89baa66 ("btrfs: scrub: switch scrub_simple_mirror() to scrub_stripe infrastructure") Tested-by: Rongrong i@rong.moe Reviewed-by: Johannes Thumshirn johannes.thumshirn@wdc.com Signed-off-by: Qu Wenruo wqu@suse.com Signed-off-by: David Sterba dsterba@suse.com [ Use min_t() to fix a compiling error due to difference types ] Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/scrub.c | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-)
--- a/fs/btrfs/scrub.c +++ b/fs/btrfs/scrub.c @@ -1099,12 +1099,22 @@ out: static void scrub_read_endio(struct btrfs_bio *bbio) { struct scrub_stripe *stripe = bbio->private; + struct bio_vec *bvec; + int sector_nr = calc_sector_number(stripe, bio_first_bvec_all(&bbio->bio)); + int num_sectors; + u32 bio_size = 0; + int i; + + ASSERT(sector_nr < stripe->nr_sectors); + bio_for_each_bvec_all(bvec, &bbio->bio, i) + bio_size += bvec->bv_len; + num_sectors = bio_size >> stripe->bg->fs_info->sectorsize_bits;
if (bbio->bio.bi_status) { - bitmap_set(&stripe->io_error_bitmap, 0, stripe->nr_sectors); - bitmap_set(&stripe->error_bitmap, 0, stripe->nr_sectors); + bitmap_set(&stripe->io_error_bitmap, sector_nr, num_sectors); + bitmap_set(&stripe->error_bitmap, sector_nr, num_sectors); } else { - bitmap_clear(&stripe->io_error_bitmap, 0, stripe->nr_sectors); + bitmap_clear(&stripe->io_error_bitmap, sector_nr, num_sectors); } bio_put(&bbio->bio); if (atomic_dec_and_test(&stripe->pending_io)) { @@ -1640,6 +1650,9 @@ static void scrub_submit_initial_read(st { struct btrfs_fs_info *fs_info = sctx->fs_info; struct btrfs_bio *bbio; + unsigned int nr_sectors = min_t(u64, BTRFS_STRIPE_LEN, stripe->bg->start + + stripe->bg->length - stripe->logical) >> + fs_info->sectorsize_bits; int mirror = stripe->mirror_num;
ASSERT(stripe->bg); @@ -1649,14 +1662,16 @@ static void scrub_submit_initial_read(st bbio = btrfs_bio_alloc(SCRUB_STRIPE_PAGES, REQ_OP_READ, fs_info, scrub_read_endio, stripe);
- /* Read the whole stripe. */ bbio->bio.bi_iter.bi_sector = stripe->logical >> SECTOR_SHIFT; - for (int i = 0; i < BTRFS_STRIPE_LEN >> PAGE_SHIFT; i++) { + /* Read the whole range inside the chunk boundary. */ + for (unsigned int cur = 0; cur < nr_sectors; cur++) { + struct page *page = scrub_stripe_get_page(stripe, cur); + unsigned int pgoff = scrub_stripe_get_page_offset(stripe, cur); int ret;
- ret = bio_add_page(&bbio->bio, stripe->pages[i], PAGE_SIZE, 0); + ret = bio_add_page(&bbio->bio, page, fs_info->sectorsize, pgoff); /* We should have allocated enough bio vectors. */ - ASSERT(ret == PAGE_SIZE); + ASSERT(ret == fs_info->sectorsize); } atomic_inc(&stripe->pending_io);