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https://github.com/kdave/btrfs-progs
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[BUG] When running lowmem mode with METADATA_ITEM which has invalid level, it will crash with the following backtrace: (gdb) bt #0 0x0000555555616b0b in btrfs_header_bytenr (eb=0x4) at ./kernel-shared/ctree.h:2134 #1 0x0000555555620c78 in check_tree_block_backref (root_id=5, bytenr=30457856, level=256) at check/mode-lowmem.c:3818 #2 0x0000555555621f6c in check_extent_item (path=0x7fffffffd9c0) at check/mode-lowmem.c:4334 #3 0x00005555556235a5 in check_leaf_items (root=0x555555688e10, path=0x7fffffffd9c0, nrefs=0x7fffffffda30, account_bytes=1) at check/mode-lowmem.c:4835 #4 0x0000555555623c6d in walk_down_tree (root=0x555555688e10, path=0x7fffffffd9c0, level=0x7fffffffd984, nrefs=0x7fffffffda30, check_all=1) at check/mode-lowmem.c:4967 #5 0x000055555562494f in check_btrfs_root (root=0x555555688e10, check_all=1) at check/mode-lowmem.c:5266 #6 0x00005555556254ee in check_chunks_and_extents_lowmem () at check/mode-lowmem.c:5556 #7 0x00005555555f0b82 in do_check_chunks_and_extents () at check/main.c:9114 #8 0x00005555555f50ea in cmd_check (cmd=0x55555567c640 <cmd_struct_check>, argc=3, argv=0x7fffffffdec0) at check/main.c:10892 #9 0x000055555556b2b1 in cmd_execute (argv=0x7fffffffdec0, argc=3, cmd=0x55555567c640 <cmd_struct_check>) at cmds/commands.h:125 [CAUSE] For function check_extent_item() it will go through inline extent items and then check their backrefs. But for METADATA_ITEM, it doesn't really validate key.offset, which is u64 and can contain value way larger than BTRFS_MAX_LEVEL (mostly caused by bit flip). In that case, if we have a larger value like 256 in key.offset, then later check_tree_block_backref() will use 256 as level, and overflow path->nodes[level] and crash. [FIX] Just verify the level, no matter if it's from btrfs_tree_block_level() (which is just u8), or it's from key.offset (which is u64). To do the check properly and detect higher bits corruption, also change the type of @level from u8 to u64. Now lowmem mode can detect the problem properly: ... [2/7] checking extents ERROR: tree block 30457856 has bad backref level, has 256 expect [0, 7] ERROR: extent[30457856 16384] level mismatch, wanted: 0, have: 256 ERROR: errors found in extent allocation tree or chunk allocation [3/7] checking free space tree ... Reviewed-by: Su Yue <l@damenly.su> Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> |
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|---|---|---|
| .. | ||
| btrfsck.h | ||
| common.h | ||
| main.c | ||
| mode-common.c | ||
| mode-common.h | ||
| mode-lowmem.c | ||
| mode-lowmem.h | ||
| mode-original.h | ||
| qgroup-verify.c | ||
| qgroup-verify.h | ||