kernel.git/fs/btrfs/backref.h, branch linux-5.12.y

btrfs: add asserts for deleting backref cache nodes

2021-02-08T21:58:56Z

A weird KASAN problem that Zygo reported could have been easily caught if we checked for basic things in our backref freeing code. We have two methods of freeing a backref node - btrfs_backref_free_node: this just is kfree() essentially. - btrfs_backref_drop_node: this actually unlinks the node and cleans up everything and then calls btrfs_backref_free_node(). We should mostly be using btrfs_backref_drop_node(), to make sure the node is properly unlinked from the backref cache, and only use btrfs_backref_free_node() when we know the node isn't actually linked to the backref cache. We made a mistake here and thus got the KASAN splat. Make this style of issue easier to find by adding some ASSERT()'s to btrfs_backref_free_node() and adjusting our deletion stuff to properly init the list so we can rely on list_empty() checks working properly. BUG: KASAN: use-after-free in btrfs_backref_cleanup_node+0x18a/0x420 Read of size 8 at addr ffff888112402950 by task btrfs/28836 CPU: 0 PID: 28836 Comm: btrfs Tainted: G W 5.10.0-e35f27394290-for-next+ #23 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 Call Trace: dump_stack+0xbc/0xf9 ? btrfs_backref_cleanup_node+0x18a/0x420 print_address_description.constprop.8+0x21/0x210 ? record_print_text.cold.34+0x11/0x11 ? btrfs_backref_cleanup_node+0x18a/0x420 ? btrfs_backref_cleanup_node+0x18a/0x420 kasan_report.cold.10+0x20/0x37 ? btrfs_backref_cleanup_node+0x18a/0x420 __asan_load8+0x69/0x90 btrfs_backref_cleanup_node+0x18a/0x420 btrfs_backref_release_cache+0x83/0x1b0 relocate_block_group+0x394/0x780 ? merge_reloc_roots+0x4a0/0x4a0 btrfs_relocate_block_group+0x26e/0x4c0 btrfs_relocate_chunk+0x52/0x120 btrfs_balance+0xe2e/0x1900 ? check_flags.part.50+0x6c/0x1e0 ? btrfs_relocate_chunk+0x120/0x120 ? kmem_cache_alloc_trace+0xa06/0xcb0 ? _copy_from_user+0x83/0xc0 btrfs_ioctl_balance+0x3a7/0x460 btrfs_ioctl+0x24c8/0x4360 ? __kasan_check_read+0x11/0x20 ? check_chain_key+0x1f4/0x2f0 ? __asan_loadN+0xf/0x20 ? btrfs_ioctl_get_supported_features+0x30/0x30 ? kvm_sched_clock_read+0x18/0x30 ? check_chain_key+0x1f4/0x2f0 ? lock_downgrade+0x3f0/0x3f0 ? handle_mm_fault+0xad6/0x2150 ? do_vfs_ioctl+0xfc/0x9d0 ? ioctl_file_clone+0xe0/0xe0 ? check_flags.part.50+0x6c/0x1e0 ? check_flags.part.50+0x6c/0x1e0 ? check_flags+0x26/0x30 ? lock_is_held_type+0xc3/0xf0 ? syscall_enter_from_user_mode+0x1b/0x60 ? do_syscall_64+0x13/0x80 ? rcu_read_lock_sched_held+0xa1/0xd0 ? __kasan_check_read+0x11/0x20 ? __fget_light+0xae/0x110 __x64_sys_ioctl+0xc3/0x100 do_syscall_64+0x37/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f4c4bdfe427 RSP: 002b:00007fff33ee6df8 EFLAGS: 00000202 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fff33ee6e98 RCX: 00007f4c4bdfe427 RDX: 00007fff33ee6e98 RSI: 00000000c4009420 RDI: 0000000000000003 RBP: 0000000000000003 R08: 0000000000000003 R09: 0000000000000078 R10: fffffffffffff59d R11: 0000000000000202 R12: 0000000000000001 R13: 0000000000000000 R14: 00007fff33ee8a34 R15: 0000000000000001 Allocated by task 28836: kasan_save_stack+0x21/0x50 __kasan_kmalloc.constprop.18+0xbe/0xd0 kasan_kmalloc+0x9/0x10 kmem_cache_alloc_trace+0x410/0xcb0 btrfs_backref_alloc_node+0x46/0xf0 btrfs_backref_add_tree_node+0x60d/0x11d0 build_backref_tree+0xc5/0x700 relocate_tree_blocks+0x2be/0xb90 relocate_block_group+0x2eb/0x780 btrfs_relocate_block_group+0x26e/0x4c0 btrfs_relocate_chunk+0x52/0x120 btrfs_balance+0xe2e/0x1900 btrfs_ioctl_balance+0x3a7/0x460 btrfs_ioctl+0x24c8/0x4360 __x64_sys_ioctl+0xc3/0x100 do_syscall_64+0x37/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Freed by task 28836: kasan_save_stack+0x21/0x50 kasan_set_track+0x20/0x30 kasan_set_free_info+0x1f/0x30 __kasan_slab_free+0xf3/0x140 kasan_slab_free+0xe/0x10 kfree+0xde/0x200 btrfs_backref_error_cleanup+0x452/0x530 build_backref_tree+0x1a5/0x700 relocate_tree_blocks+0x2be/0xb90 relocate_block_group+0x2eb/0x780 btrfs_relocate_block_group+0x26e/0x4c0 btrfs_relocate_chunk+0x52/0x120 btrfs_balance+0xe2e/0x1900 btrfs_ioctl_balance+0x3a7/0x460 btrfs_ioctl+0x24c8/0x4360 __x64_sys_ioctl+0xc3/0x100 do_syscall_64+0x37/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xa9 The buggy address belongs to the object at ffff888112402900 which belongs to the cache kmalloc-128 of size 128 The buggy address is located 80 bytes inside of 128-byte region [ffff888112402900, ffff888112402980) The buggy address belongs to the page: page:0000000028b1cd08 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888131c810c0 pfn:0x112402 flags: 0x17ffe0000000200(slab) raw: 017ffe0000000200 ffffea000424f308 ffffea0007d572c8 ffff888100040440 raw: ffff888131c810c0 ffff888112402000 0000000100000009 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888112402800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888112402880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888112402900: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888112402980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888112402a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb Link: https://lore.kernel.org/linux-btrfs/20201208194607.GI31381@hungrycats.org/ CC: stable@vger.kernel.org # 5.10+ Signed-off-by: Josef Bacik Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: rename BTRFS_ROOT_REF_COWS to BTRFS_ROOT_SHAREABLE

2020-05-25T09:25:35Z

The name BTRFS_ROOT_REF_COWS is not very clear about the meaning. In fact, that bit can only be set to those trees: - Subvolume roots - Data reloc root - Reloc roots for above roots All other trees won't get this bit set. So just by the result, it is obvious that, roots with this bit set can have tree blocks shared with other trees. Either shared by snapshots, or by reloc roots (an special snapshot created by relocation). This patch will rename BTRFS_ROOT_REF_COWS to BTRFS_ROOT_SHAREABLE to make it easier to understand, and update all comment mentioning "reference counted" to follow the rename. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: reloc: move error handling of build_backref_tree() to backref.c

2020-05-25T09:25:21Z

The error cleanup will be extracted as a new function, btrfs_backref_error_cleanup(), and moved to backref.c and exported for later usage. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: backref: rename and move finish_upper_links()

2020-05-25T09:25:21Z

This the the 2nd major part of generic backref cache. Move it to backref.c so we can reuse it. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: backref: rename and move handle_one_tree_block()

2020-05-25T09:25:21Z

This function is the major part of backref cache build process, move it to backref.c so we can reuse it later. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: backref: rename and move backref_tree_panic()

2020-05-25T09:25:21Z

Also change the parameter, since all callers can easily grab an fs_info, there is no need for all the pointer chasing. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: backref: rename and move backref_cache_cleanup()

2020-05-25T09:25:20Z

Since we're releasing all existing nodes/edges, other than cleanup the mess after error, "release" is a more proper naming here. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: backref: rename and move remove_backref_node()

2020-05-25T09:25:20Z

Also add comment explaining the cleanup progress, to differ it from btrfs_backref_drop_node(). Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: backref: rename and move drop_backref_node()

2020-05-25T09:25:20Z

With extra comment for drop_backref_node() as it has some similarity with remove_backref_node(), thus we need extra comment explaining the difference. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: backref: rename and move free_backref_(node|edge)

2020-05-25T09:25:20Z

Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba