Message ID | 20220117023850.40337-2-wqu@suse.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | btrfs-progs: fsck: detect obviously invalid metadata backref level | expand |
On Mon 17 Jan 2022 at 10:38, Qu Wenruo <wqu@suse.com> wrote: > [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 > ... > > Signed-off-by: Qu Wenruo <wqu@suse.com> > Reviewed-by: Su Yue <l@damenly.su> -- Su > --- > check/mode-lowmem.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/check/mode-lowmem.c b/check/mode-lowmem.c > index cc6773cd4d0c..99f519631a50 100644 > --- a/check/mode-lowmem.c > +++ b/check/mode-lowmem.c > @@ -4242,7 +4242,7 @@ static int check_extent_item(struct > btrfs_path *path) > u64 owner_offset; > u64 super_gen; > int metadata = 0; > - int level; > + u64 level; /* To handle corrupted values in skinny > backref */ > struct btrfs_key key; > int ret; > int err = 0; > @@ -4303,6 +4303,16 @@ static int check_extent_item(struct > btrfs_path *path) > /* New METADATA_ITEM */ > level = key.offset; > } > + > + if (metadata && level >= BTRFS_MAX_LEVEL) { > + error( > + "tree block %llu has bad backref level, has %llu expect > [0, %u]", > + key.objectid, level, BTRFS_MAX_LEVEL - 1); > + err |= BACKREF_MISMATCH; > + /* This is a critical error, exit right now */ > + goto out; > + } > + > ptr_offset = ptr - (unsigned long)ei; > > next:
diff --git a/check/mode-lowmem.c b/check/mode-lowmem.c index cc6773cd4d0c..99f519631a50 100644 --- a/check/mode-lowmem.c +++ b/check/mode-lowmem.c @@ -4242,7 +4242,7 @@ static int check_extent_item(struct btrfs_path *path) u64 owner_offset; u64 super_gen; int metadata = 0; - int level; + u64 level; /* To handle corrupted values in skinny backref */ struct btrfs_key key; int ret; int err = 0; @@ -4303,6 +4303,16 @@ static int check_extent_item(struct btrfs_path *path) /* New METADATA_ITEM */ level = key.offset; } + + if (metadata && level >= BTRFS_MAX_LEVEL) { + error( + "tree block %llu has bad backref level, has %llu expect [0, %u]", + key.objectid, level, BTRFS_MAX_LEVEL - 1); + err |= BACKREF_MISMATCH; + /* This is a critical error, exit right now */ + goto out; + } + ptr_offset = ptr - (unsigned long)ei; next:
[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 ... Signed-off-by: Qu Wenruo <wqu@suse.com> --- check/mode-lowmem.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)