kernel/git/stable/linux.git/fs/btrfs/relocation.c, branch master

btrfs: drop recovered reloc root refs on recovery failure

2026-08-07T17:17:17+00:00

During relocation recovery, each fs root gets a reference to its relocation root. If loading or adding a later root fails, or if the first transaction commit fails, btrfs_recover_relocation() jumps to out_unset before merge_reloc_roots() and clean_dirty_subvols(). put_reloc_control() drops the list-owned relocation root references, but it does not clear fs_root->reloc_root or drop the references owned by those pointers. Mount cleanup only drops them when BTRFS_FS_ERROR is set, so an error such as -ENOMEM while processing a later root can leave references behind. Keep temporary references to the fs roots associated during recovery. On failure, clear their reloc_root pointers and drop the corresponding references. Once the first transaction commit succeeds, drop only the temporary fs root references and let the normal merge and cleanup paths handle the relocation roots. Fault injection on a pending-relocation image confirmed the cleanup gap. With an injected first-commit failure, 25 fs roots had reloc_root set with fs_error=0. With this fix, the same failure path drops that count to 0 before mount fails. Fixes: f44deb7442ed ("btrfs: hold a ref on the root->reloc_root") CC: stable@vger.kernel.org Signed-off-by: Guanghui Yang <3497809730@qq.com> Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: zoned: don't force read-only on transient -EAGAIN from reloc merge

2026-08-07T17:16:28+00:00

On a zoned FS, btrfs_delayed_refs_rsv_refill() returns -EAGAIN whenever the over-committed metadata plus the zone_unusable bytes exceeds the usable size in a metadata block-group to avoid heavy over-commit of metadata and early ENOSPC in one transaction. If this happens while doing reclaim, the transaction is getting aborted. Treat -EAGAIN as a soft, retryable condition in case of block-group reclaim. Reported-by: Damien Le Moal Fixes: 7bcb04de982f ("btrfs: zoned: cap delayed refs metadata reservation to avoid overcommit") Reviewed-by: Filipe Manana Signed-off-by: Johannes Thumshirn Signed-off-by: David Sterba

btrfs: fix copy_remapped_data() to not allocate more memory than intended

2026-08-07T17:16:27+00:00

The loop intends to copy the data in chunks up to 1M but we allocate the pages array for the entire length and don't cap it to 1M. Fix this by computing 'nr_pages' using 'copy_len' instead of 'length'. While at it, also make 'nr_pages' and 'copy_len' const, as they never change, to make the code more clear. Reviewed-by: Johannes Thumshirn Signed-off-by: Filipe Manana Signed-off-by: David Sterba

btrfs: fix memory barrier order in reloc_root_is_dead()

2026-08-07T17:16:27+00:00

When we set a root's reloc_root to NULL, we do it like this: static void clear_reloc_root(struct btrfs_root *root) { root->reloc_root = NULL; /* * Need barrier to ensure clear_bit() only happens after * root->reloc_root = NULL. Pairs with have_reloc_root(). */ smp_wmb(); clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state); } So that a NULL reloc_root is always seen before seeing that the bit BTRFS_ROOT_DEAD_RELOC_TREE was cleared. But on the read side we have: static bool reloc_root_is_dead(const struct btrfs_root *root) { smp_rmb(); if (test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state)) return true; return false; } And then callers of reloc_root_is_dead() access root->reloc_root. Because the read memory barrier is placed before testing the bit, the CPU is completely free to speculatively reorder those two loads. It can read root->reloc_root before it actually checks the dead tree bit. Sashiko reported this as an existing problem in another patch review, see the link in the Link tag below. Fix this by moving the read memory barrier to happen after testing the bit and update the comment to reflect current reality. Link: https://sashiko.dev/#/patchset/cf84f1a217c719e25b6b69e4298dd7afd36c9427.1781194426.git.fdmanana%40suse.com Reviewed-by: Boris Burkov Signed-off-by: Filipe Manana Signed-off-by: David Sterba

btrfs: free mapping node on duplicate reloc root insert

2026-07-14T05:05:00+00:00

__add_reloc_root() allocates a mapping_node before inserting it into rc->reloc_root_tree. If rb_simple_insert() finds an existing entry, it returns the existing rb_node and leaves the newly allocated node unlinked. The error path then returns -EEXIST without freeing the new node. Since the node was never inserted into reloc_root_tree, the later cleanup in put_reloc_control() cannot find it either. Free the newly allocated node before returning -EEXIST. The callers currently assert that -EEXIST should not happen, so this is a defensive cleanup for an unexpected duplicate insert path. If the path is ever reached, the local allocation should still be released. Fixes: 57a304cfd43b ("btrfs: do not panic in __add_reloc_root") Reviewed-by: Qu Wenruo Signed-off-by: Guanghui Yang <3497809730@qq.com> Signed-off-by: David Sterba

btrfs: reject inline file extents item in get_new_location()

2026-07-14T05:03:15+00:00

Commit a6908f88c9da ("btrfs: validate data reloc tree file extent item members") introduced extra checks on file extent items for data reloc inodes, but it checked the file extent offset without checking if the file extent is inlined. This can lead to either false alerts (as the offset member is inside the inlined data) or even reading beyond the item range. This has already triggered a warning in a syzbot report. Although the root fix is to avoid compression for data reloc inodes, for the sake of consistency, reject inlined file extents first. Fixes: a6908f88c9da ("btrfs: validate data reloc tree file extent item members") CC: stable@vger.kernel.org Reviewed-by: Filipe Manana Signed-off-by: Qu Wenruo Signed-off-by: David Sterba

btrfs: fix reloc root cleanup in merge_reloc_roots()

2026-07-14T05:02:13+00:00

If the root we got has zero root refs in its root item, we are resetting the root's ->reloc_root without using barriers like we do everywhere else. Sashiko complained about this while reviewing another patch, and it's correct (see the Link tag below). Also, we should not clear BTRFS_ROOT_DEAD_RELOC_TREE from the root unless the root points to the reloc root we have. Fix this by using clear_reloc_root(), which issues the memory barrier after setting the root's ->reloc_root to NULL and before clearing the bit BTRFS_ROOT_DEAD_RELOC_TREE from the root. Link: https://sashiko.dev/#/patchset/cf84f1a217c719e25b6b69e4298dd7afd36c9427.1781194426.git.fdmanana%40suse.com Reviewed-by: Boris Burkov Signed-off-by: Filipe Manana Signed-off-by: David Sterba

btrfs: fix use-after-free on reloc root after error in insert_dirty_subvol()

2026-07-14T05:01:55+00:00

If during relocation we fail in insert_dirty_subvol() because btrfs_update_reloc_root() returned an error, we will leave a root's reloc_root field pointing to a reloc root that was freed instead of NULL, resulting later in a use-after-free, or double free attempt during unmount. The sequence of steps is this: 1) During relocation the call to btrfs_update_reloc_root() in insert_dirty_subvol() fails, so insert_dirty_subvol() returns the error to merge_reloc_root() without adding the root to the list rc->dirty_subvol_roots; 2) Then merge_reloc_root() aborts the current transaction because insert_dirty_subvol() returned an error; 3) Up the call chain, merge_reloc_roots() gets the error, adds the reloc root for root X to the local reloc_roots list and jumps to the 'out' label, where it calls free_reloc_roots() to free all the reloc roots in the local reloc_roots list. This frees the reloc root for root X; 4) We go up the call chain to relocate_block_group() which calls clean_dirty_subvols() to go over dirty roots and set their ->reloc_root field to NULL, but root X is not in the dirty_subvol_roots list, so its ->reloc_root still points to a reloc root; 5) Relocation finishes, with an error and a transaction abort, but the ->reloc_root field for root X still points to the reloc root that was freed in step 3; 6) When unmounting the fs we end up calling: btrfs_free_fs_roots() btrfs_drop_and_free_fs_root() --> calls btrfs_put_root() against root X's ->reloc_root which is not NULL and points to the already freed reloc root in step 4 above Resulting in a use-after-free to a double free attempt. Syzbot reported this with the following dmesg/syslog: [ 106.004389][ T5339] BTRFS error (device loop0 state A): Transaction aborted (error -5) [ 106.014266][ T5339] BTRFS: error (device loop0 state A) in merge_reloc_root:1655: errno=-5 IO failure [ 106.021891][ T1061] BTRFS error (device loop0 state A): error while writing out transaction: -5 [ 106.026964][ T1061] BTRFS warning (device loop0 state A): Skipping commit of aborted transaction. [ 106.033807][ T5340] BTRFS error (device loop0 state A): bdev /dev/loop0 errs: wr 3, rd 0, flush 0, corrupt 0, gen 0 [ 106.039265][ T1061] BTRFS: error (device loop0 state A) in cleanup_transaction:2067: errno=-5 IO failure [ 106.044382][ T5339] BTRFS info (device loop0 state EA): forced readonly [ 106.074329][ T5339] BTRFS: error (device loop0 state EA) in merge_reloc_roots:1887: errno=-5 IO failure [ 106.081004][ T5356] BTRFS info (device loop0 state EA): scrub: started on devid 1 [ 106.085611][ T5339] BTRFS info (device loop0 state EA): balance: ended with status: -30 [ 106.089517][ T5356] BTRFS info (device loop0 state EA): scrub: not finished on devid 1 with status: -30 [ 106.662365][ T5338] BTRFS info (device loop0 state EA): last unmount of filesystem 3a375e4e-b156-4d76-a2ad-16e198ce1409 [ 106.682946][ T5338] ================================================================== [ 106.686574][ T5338] BUG: KASAN: slab-use-after-free in btrfs_put_root+0x2f/0x250 [ 106.690090][ T5338] Write of size 4 at addr ffff88803f978630 by task syz.0.0/5338 [ 106.693173][ T5338] [ 106.694279][ T5338] CPU: 0 UID: 0 PID: 5338 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) [ 106.694293][ T5338] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 106.694300][ T5338] Call Trace: [ 106.694308][ T5338] [ 106.694314][ T5338] dump_stack_lvl+0xe8/0x150 [ 106.694331][ T5338] print_address_description+0x55/0x1e0 [ 106.694343][ T5338] ? btrfs_put_root+0x2f/0x250 [ 106.694358][ T5338] print_report+0x58/0x70 [ 106.694368][ T5338] kasan_report+0x117/0x150 [ 106.694384][ T5338] ? btrfs_put_root+0x2f/0x250 [ 106.694399][ T5338] kasan_check_range+0x264/0x2c0 [ 106.694416][ T5338] btrfs_put_root+0x2f/0x250 [ 106.694430][ T5338] btrfs_drop_and_free_fs_root+0x160/0x210 [ 106.694447][ T5338] btrfs_free_fs_roots+0x2f9/0x3c0 [ 106.694464][ T5338] ? __pfx_btrfs_free_fs_roots+0x10/0x10 [ 106.694479][ T5338] ? free_root_pointers+0x5bf/0x5f0 [ 106.694494][ T5338] close_ctree+0x798/0x12d0 [ 106.694511][ T5338] ? __pfx_close_ctree+0x10/0x10 [ 106.694526][ T5338] ? _raw_spin_unlock_irqrestore+0x74/0x80 [ 106.694599][ T5338] ? rcu_preempt_deferred_qs_irqrestore+0x906/0xbc0 [ 106.694620][ T5338] ? __rcu_read_unlock+0x83/0xe0 [ 106.694636][ T5338] ? btrfs_put_super+0x48/0x1c0 [ 106.694652][ T5338] ? __pfx_btrfs_put_super+0x10/0x10 [ 106.694667][ T5338] generic_shutdown_super+0x13d/0x2d0 [ 106.694682][ T5338] kill_anon_super+0x3b/0x70 [ 106.694695][ T5338] btrfs_kill_super+0x41/0x50 [ 106.694710][ T5338] deactivate_locked_super+0xbc/0x130 [ 106.694722][ T5338] cleanup_mnt+0x437/0x4d0 [ 106.694736][ T5338] ? _raw_spin_unlock_irq+0x23/0x50 [ 106.694752][ T5338] task_work_run+0x1d9/0x270 [ 106.694769][ T5338] ? __pfx_task_work_run+0x10/0x10 [ 106.694784][ T5338] ? do_raw_spin_unlock+0x4d/0x210 [ 106.694802][ T5338] do_exit+0x70f/0x22c0 [ 106.694817][ T5338] ? trace_irq_disable+0x3b/0x140 [ 106.694835][ T5338] ? __pfx_do_exit+0x10/0x10 [ 106.694848][ T5338] ? preempt_schedule_thunk+0x16/0x30 [ 106.694863][ T5338] ? preempt_schedule_common+0x82/0xd0 [ 106.694878][ T5338] ? preempt_schedule_thunk+0x16/0x30 [ 106.694892][ T5338] do_group_exit+0x21b/0x2d0 [ 106.694906][ T5338] ? entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 106.694918][ T5338] __x64_sys_exit_group+0x3f/0x40 [ 106.694932][ T5338] x64_sys_call+0x221a/0x2240 [ 106.694944][ T5338] do_syscall_64+0x174/0x580 [ 106.694954][ T5338] ? clear_bhb_loop+0x40/0x90 [ 106.694967][ T5338] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 106.694978][ T5338] RIP: 0033:0x7f958ef9ce59 [ 106.694988][ T5338] Code: Unable to access opcode bytes at 0x7f958ef9ce2f. [ 106.694994][ T5338] RSP: 002b:00007fffd4058318 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 [ 106.695008][ T5338] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f958ef9ce59 [ 106.695015][ T5338] RDX: 00007f958c3f8000 RSI: 0000000000000000 RDI: 0000000000000000 [ 106.695022][ T5338] RBP: 0000000000000003 R08: 0000000000000000 R09: 00007f958f1e73e0 [ 106.695028][ T5338] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 [ 106.695034][ T5338] R13: 00007f958f1e73e0 R14: 0000000000000003 R15: 00007fffd40583d0 [ 106.695046][ T5338] [ 106.695050][ T5338] [ 106.821635][ T5338] Allocated by task 1061: [ 106.823446][ T5338] kasan_save_track+0x3e/0x80 [ 106.825498][ T5338] __kasan_kmalloc+0x93/0xb0 [ 106.827381][ T5338] __kmalloc_cache_noprof+0x31c/0x660 [ 106.829525][ T5338] btrfs_alloc_root+0x75/0x930 [ 106.831458][ T5338] read_tree_root_path+0x127/0xb00 [ 106.833556][ T5338] btrfs_read_tree_root+0x34/0x60 [ 106.835553][ T5338] create_reloc_root+0x6b3/0xcb0 [ 106.837556][ T5338] btrfs_init_reloc_root+0x2ec/0x4b0 [ 106.839557][ T5338] record_root_in_trans+0x2ab/0x350 [ 106.841685][ T5338] btrfs_record_root_in_trans+0x15c/0x180 [ 106.844237][ T5338] start_transaction+0x39c/0x1820 [ 106.846638][ T5338] btrfs_finish_one_ordered+0x88e/0x2680 [ 106.849436][ T5338] btrfs_work_helper+0x37b/0xc20 [ 106.851549][ T5338] process_scheduled_works+0xb5d/0x1860 [ 106.853807][ T5338] worker_thread+0xa53/0xfc0 [ 106.855773][ T5338] kthread+0x389/0x470 [ 106.857548][ T5338] ret_from_fork+0x514/0xb70 [ 106.859493][ T5338] ret_from_fork_asm+0x1a/0x30 [ 106.861504][ T5338] [ 106.862527][ T5338] Freed by task 5339: [ 106.864224][ T5338] kasan_save_track+0x3e/0x80 [ 106.866180][ T5338] kasan_save_free_info+0x46/0x50 [ 106.868371][ T5338] __kasan_slab_free+0x5c/0x80 [ 106.870462][ T5338] kfree+0x1c5/0x640 [ 106.872180][ T5338] __del_reloc_root+0x341/0x3b0 [ 106.874290][ T5338] free_reloc_roots+0x5f/0x90 [ 106.876282][ T5338] merge_reloc_roots+0x73f/0x8a0 [ 106.878489][ T5338] relocate_block_group+0xbcc/0xe70 [ 106.880742][ T5338] do_nonremap_reloc+0xa8/0x5b0 [ 106.882885][ T5338] btrfs_relocate_block_group+0x7e6/0xc40 [ 106.885336][ T5338] btrfs_relocate_chunk+0x115/0x820 [ 106.887502][ T5338] __btrfs_balance+0x1db0/0x2ae0 [ 106.889543][ T5338] btrfs_balance+0xaf3/0x11b0 [ 106.891456][ T5338] btrfs_ioctl_balance+0x3d3/0x610 [ 106.893672][ T5338] __se_sys_ioctl+0xfc/0x170 [ 106.895530][ T5338] do_syscall_64+0x174/0x580 [ 106.897518][ T5338] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 106.900101][ T5338] [ 106.901123][ T5338] The buggy address belongs to the object at ffff88803f978000 [ 106.901123][ T5338] which belongs to the cache kmalloc-4k of size 4096 [ 106.906907][ T5338] The buggy address is located 1584 bytes inside of [ 106.906907][ T5338] freed 4096-byte region [ffff88803f978000, ffff88803f979000) [ 106.912980][ T5338] [ 106.914022][ T5338] The buggy address belongs to the physical page: [ 106.916716][ T5338] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3f978 [ 106.920390][ T5338] head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 [ 106.923834][ T5338] flags: 0x4fff00000000040(head|node=1|zone=1|lastcpupid=0x7ff) [ 106.927104][ T5338] page_type: f5(slab) [ 106.928898][ T5338] raw: 04fff00000000040 ffff88801ac42140 dead000000000122 0000000000000000 [ 106.932507][ T5338] raw: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000 [ 106.936193][ T5338] head: 04fff00000000040 ffff88801ac42140 dead000000000122 0000000000000000 [ 106.939856][ T5338] head: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000 [ 106.943601][ T5338] head: 04fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff [ 106.947268][ T5338] head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008 [ 106.950988][ T5338] page dumped because: kasan: bad access detected [ 106.953710][ T5338] page_owner tracks the page as allocated [ 106.956198][ T5338] page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 24, tgid 24 (kworker/u4:2), ts 105728970387, free_ts 29540875453 [ 106.964984][ T5338] post_alloc_hook+0x22d/0x280 [ 106.966956][ T5338] get_page_from_freelist+0x2593/0x2610 [ 106.969307][ T5338] __alloc_frozen_pages_noprof+0x18d/0x380 [ 106.971839][ T5338] allocate_slab+0x77/0x660 [ 106.973709][ T5338] refill_objects+0x339/0x3d0 [ 106.975696][ T5338] __pcs_replace_empty_main+0x321/0x720 [ 106.978136][ T5338] __kmalloc_node_track_caller_noprof+0x572/0x7b0 [ 106.981009][ T5338] __alloc_skb+0x2c1/0x7d0 [ 106.982983][ T5338] nsim_dev_trap_report_work+0x29a/0xb90 [ 106.985356][ T5338] process_scheduled_works+0xb5d/0x1860 [ 106.987710][ T5338] worker_thread+0xa53/0xfc0 [ 106.989847][ T5338] kthread+0x389/0x470 [ 106.991727][ T5338] ret_from_fork+0x514/0xb70 [ 106.993722][ T5338] ret_from_fork_asm+0x1a/0x30 [ 106.995900][ T5338] page last free pid 77 tgid 77 stack trace: [ 106.998479][ T5338] __free_frozen_pages+0xc1c/0xd30 [ 107.000819][ T5338] vfree+0x1d1/0x2f0 [ 107.002631][ T5338] delayed_vfree_work+0x55/0x80 [ 107.004848][ T5338] process_scheduled_works+0xb5d/0x1860 [ 107.007366][ T5338] worker_thread+0xa53/0xfc0 [ 107.009388][ T5338] kthread+0x389/0x470 [ 107.011177][ T5338] ret_from_fork+0x514/0xb70 [ 107.013313][ T5338] ret_from_fork_asm+0x1a/0x30 [ 107.015454][ T5338] [ 107.016460][ T5338] Memory state around the buggy address: [ 107.019052][ T5338] ffff88803f978500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 107.022691][ T5338] ffff88803f978580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 107.026264][ T5338] >ffff88803f978600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 107.029721][ T5338] ^ [ 107.032062][ T5338] ffff88803f978680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 107.035547][ T5338] ffff88803f978700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 107.038865][ T5338] ================================================================== Fix this by resetting a root's ->reloc_root if we get an error while trying to merge a reloc root. Reported-by: syzbot+b3d472d13f9d7bf20669@syzkaller.appspotmail.com Link: https://lore.kernel.org/linux-btrfs/6a1ebde9.c1435f33.112120.0176.GAE@google.com/ Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Signed-off-by: David Sterba

btrfs: decentralize transaction aborts in create_reloc_root()

2026-06-30T00:02:02+00:00

Decentralize transaction aborts in create_reloc_root(), so that it is obvious which call failed and what caused the transaction abort. Reviewed-by: Filipe Manana Signed-off-by: Johannes Thumshirn Signed-off-by: David Sterba

btrfs: fix root leak if its reloc root is unexpected in merge_reloc_roots()

2026-06-29T23:59:13+00:00

If we have an unexpected reloc_root for our root, we jump to the out label but never drop the reference we obtained for root, resulting in a leak. Add a missing btrfs_put_root() call. Fixes: 24213fa46c70 ("btrfs: do proper error handling in merge_reloc_roots") Reviewed-by: Qu Wenruo Reviewed-by: Johannes Thumshirn Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba