kernel/git/stable/linux.git/fs/btrfs/backref.c, branch linux-7.2.y

btrfs: fix NULL pointer deref during assertion in btrfs_backref_free_node()

2026-07-14T05:04:10+00:00

In btrfs_backref_free_node() we have the following assertion: ASSERT(node->eb == NULL, "node->eb->start=%llu", node->eb->start); and a user reported the following crash: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 0 UID: 0 PID: 10422 Comm: syz.0.17 Not tainted 7.1.0-02765-g6b5a2b7d9bc1-dirty #44 PREEMPT(full) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:btrfs_backref_free_node fs/btrfs/backref.c:3057 [inline] RIP: 0010:btrfs_backref_free_node+0xb9/0x200 fs/btrfs/backref.c:3051 Code: 00 fc ff (...) RSP: 0018:ffa0000006b0f3c0 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff840eb78b RDX: 0000000000000000 RSI: ffffffff840eafa5 RDI: ff110000742ab768 RBP: ff110000742ab700 R08: 0000000000000000 R09: 0000000000000000 R10: ff110000742ab700 R11: 00000000000a81f9 R12: ff11000107a92020 R13: ff1100005c182ea8 R14: 0000000000000000 R15: dffffc0000000000 FS: 0000555575536500(0000) GS:ff11000183985000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa3d0e9d580 CR3: 000000002232a000 CR4: 0000000000753ef0 PKRU: 00000000 Call Trace: btrfs_backref_cleanup_node+0x27/0x30 fs/btrfs/backref.c:3133 relocate_tree_block fs/btrfs/relocation.c:2604 [inline] relocate_tree_blocks+0x11b0/0x1a20 fs/btrfs/relocation.c:2707 relocate_block_group+0x499/0xf30 fs/btrfs/relocation.c:3635 do_nonremap_reloc fs/btrfs/relocation.c:5323 [inline] btrfs_relocate_block_group+0x1749/0x5fb0 fs/btrfs/relocation.c:5490 btrfs_relocate_chunk+0x12b/0x950 fs/btrfs/volumes.c:3647 __btrfs_balance fs/btrfs/volumes.c:4586 [inline] btrfs_balance+0x1c7f/0x55c0 fs/btrfs/volumes.c:4973 btrfs_ioctl_balance fs/btrfs/ioctl.c:3474 [inline] btrfs_ioctl+0x38a4/0x5d20 fs/btrfs/ioctl.c:5570 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x11f/0x860 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fb38e3b56dd Code: 02 b8 ff (...) RSP: 002b:00007fff04115788 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fb38f6b0020 RCX: 00007fb38e3b56dd RDX: 00002000000003c0 RSI: 00000000c4009420 RDI: 0000000000000004 RBP: 00007fb38e451b48 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007fb38f6b0020 R15: 00007fb38f6b002c It seems that this happens on some systems for some reason, when the ASSERT() macro calls the inline function verify_assert_printk_format() to evaluate the format string and arguments, causing the NULL pointer dereference on node->eb. So change the assertion to check for a NULL node->eb before dereferencing it. Also, while at it, make the assertion more useful by printing the owner of the extent buffer as well as its level. Reported-by: Yue Sun Link: https://lore.kernel.org/linux-btrfs/20260626065542.38413-1-samsun1006219@gmail.com/ Fixes: c4e7778580d6 ("btrfs: use verbose assertions in backref.c") Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: use verbose assertions in backref.c

2026-06-09T16:22:46+00:00

While debugging a relocation issue I hit an assertion in backref.c but it was not super useful, since it could not tell what was the unexpected value that triggered the assertion. The stack trace was this: [583246.338097] assertion failed: !cache->nr_nodes, in fs/btrfs/backref.c:3158 [583246.339588] ------------[ cut here ]------------ [583246.340573] kernel BUG at fs/btrfs/backref.c:3158! [583246.342075] Oops: invalid opcode: 0000 [#1] SMP PTI [583246.343294] CPU: 5 UID: 0 PID: 677957 Comm: btrfs Not tainted 7.1.0-rc4-btrfs-next-234+ #1 PREEMPT(full) [583246.345715] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014 [583246.348694] RIP: 0010:btrfs_backref_release_cache.cold+0x61/0x84 [btrfs] [583246.350759] Code: 90 d5 7c (...) [583246.354923] RSP: 0018:ffffd4fc88c93ad8 EFLAGS: 00010246 [583246.355982] RAX: 000000000000003e RBX: ffff8dec90d97020 RCX: 0000000000000000 [583246.357459] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00000000ffffffff [583246.359517] RBP: ffff8dec8eeb78c0 R08: 0000000000000000 R09: 3fffffffffefffff [583246.361180] R10: ffffd4fc88c93970 R11: 0000000000000003 R12: ffff8decd21f3470 [583246.363184] R13: 00000000fffffffe R14: ffff8decd21f3000 R15: ffff8decd21f3000 [583246.364666] FS: 00007f9a51751400(0000) GS:ffff8df3f4255000(0000) knlGS:0000000000000000 [583246.366287] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [583246.367443] CR2: 00007f9a518ed8f5 CR3: 00000004467c8002 CR4: 0000000000370ef0 [583246.368969] Call Trace: [583246.369541] [583246.370040] relocate_block_group+0xf2/0x520 [btrfs] [583246.371243] btrfs_relocate_block_group+0x9a9/0x22e0 [btrfs] [583246.372443] ? preempt_count_add+0x47/0xa0 [583247.532978] ? btrfs_tree_read_lock_nested+0x19/0x90 [btrfs] [583247.534520] ? mutex_lock+0x1a/0x40 [583247.602233] ? btrfs_scrub_pause+0x2e/0x120 [btrfs] [583247.603543] btrfs_relocate_chunk+0x3b/0x1a0 [btrfs] [583247.604893] btrfs_balance+0x9d5/0x1920 [btrfs] [583247.606189] ? preempt_count_add+0x69/0xa0 [583247.607030] btrfs_ioctl+0x260c/0x2a20 [btrfs] [583247.608015] ? __memcg_slab_free_hook+0x156/0x1a0 [583247.636971] __x64_sys_ioctl+0x92/0xe0 [583247.679247] do_syscall_64+0x60/0xf20 [583247.753297] ? clear_bhb_loop+0x60/0xb0 [583247.756321] entry_SYSCALL_64_after_hwframe+0x76/0x7e [583247.787018] RIP: 0033:0x7f9a5186a8db [583247.787787] Code: 00 48 89 (...) [583247.791410] RSP: 002b:00007fff2ffa6ac0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [583247.792897] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f9a5186a8db [583247.794319] RDX: 00007fff2ffa6bb0 RSI: 00000000c4009420 RDI: 0000000000000003 [583247.795714] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [583247.797149] R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff2ffa903f [583247.798685] R13: 00007fff2ffa6bb0 R14: 0000000000000002 R15: 0000000000000002 [583247.800136] So update all simple assertions in backref.c to print out the values when they aren't testing simple boolean conditions. Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Signed-off-by: David Sterba

btrfs: use on stack backref iterator in build_backref_tree()

2026-06-08T13:53:32+00:00

The iterator is used only once and within build_backref_tree() so we can avoid one allocation and place it on stack. Signed-off-by: David Sterba

btrfs: remove fs_info from struct btrfs_backref_iter

2026-06-08T13:53:32+00:00

The fs_info is available everywhere and we don't need to store it inside a structure that is used within one function only, which is build_backref_tree(). The size of btrfs_backref_iter is now 48 bytes. Signed-off-by: David Sterba

btrfs: make more ASSERTs verbose, part 3

2026-06-08T13:53:28+00:00

We have support for optional string to be printed in ASSERT() (added in 19468a623a9109 ("btrfs: enhance ASSERT() to take optional format string")), it's not yet everywhere it could be so add a few more files. Try to finish what was left after 1c094e6ccead7a ("btrfs: make a few more ASSERTs verbose"). Signed-off-by: David Sterba

btrfs: remove redundant extent_buffer_uptodate() checks after read_tree_block()

2026-04-07T16:55:55+00:00

We have several places that call extent_buffer_uptodate() after reading a tree block with read_tree_block(), but that is redundant since we already call extent_buffer_uptodate() in the call chain of read_tree_block(): read_tree_block() btrfs_read_extent_buffer() read_extent_buffer_pages() returns -EIO if extent_buffer_uptodate() returns false So remove those redundant checks. Reviewed-by: Boris Burkov Signed-off-by: Filipe Manana Signed-off-by: David Sterba

Merge tag 'for-7.0-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

2026-03-21T15:42:17+00:00

Pull btrfs fixes from David Sterba: "Another batch of fixes for problems that have been identified by tools analyzing code or by fuzzing. Most of them are short, two patches fix the same thing in many places so the diffs are bigger. - handle potential NULL pointer errors after attempting to read extent and checksum trees - prevent ENOSPC when creating many qgroups by ioctls in the same transaction - encoded write ioctl fixes (with 64K page and 4K block size): - fix unexpected bio length - do not let compressed bios and pages interfere with page cache - compression fixes on setups with 64K page and 4K block size: fix folio length assertions (zstd and lzo) - remap tree fixes: - make sure to hold block group reference while moving it - handle early exit when moving block group to unused list - handle deleted subvolumes with inconsistent state of deletion progress" * tag 'for-7.0-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: btrfs: reject root items with drop_progress and zero drop_level btrfs: check block group before marking it unused in balance_remap_chunks() btrfs: hold block group reference during entire move_existing_remap() btrfs: fix an incorrect ASSERT() condition inside lzo_decompress_bio() btrfs: fix an incorrect ASSERT() condition inside zstd_decompress_bio() btrfs: do not touch page cache for encoded writes btrfs: fix a bug that makes encoded write bio larger than expected btrfs: reserve enough transaction items for qgroup ioctls btrfs: check for NULL root after calls to btrfs_csum_root() btrfs: check for NULL root after calls to btrfs_extent_root()

btrfs: check for NULL root after calls to btrfs_extent_root()

2026-03-17T10:22:49+00:00

btrfs_extent_root() can return a NULL pointer in case the root we are looking for is not in the rb tree that tracks roots. So add checks to every caller that is missing such check to log a message and return an error. The same applies to callers of btrfs_block_group_root(), since it calls btrfs_extent_root(). Reported-by: Chris Mason Link: https://lore.kernel.org/linux-btrfs/20260208161657.3972997-1-clm@meta.com/ Reviewed-by: Boris Burkov Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This was done entirely with mindless brute force, using git grep -l '\

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook