From: Su Yue <l@damenly.su>
To: Qu Wenruo <wqu@suse.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 1/3] btrfs-progs: check/lowmem: fix crash when METADATA_ITEM has invalid level
Date: Mon, 17 Jan 2022 10:47:20 +0800 [thread overview]
Message-ID: <5yqjw00x.fsf@damenly.su> (raw)
In-Reply-To: <20220117023850.40337-2-wqu@suse.com>
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:
next prev parent reply other threads:[~2022-01-17 2:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-17 2:38 [PATCH 0/3] btrfs-progs: fsck: detect obviously invalid metadata backref level Qu Wenruo
2022-01-17 2:38 ` [PATCH 1/3] btrfs-progs: check/lowmem: fix crash when METADATA_ITEM has invalid level Qu Wenruo
2022-01-17 2:47 ` Su Yue [this message]
2022-01-17 2:38 ` [PATCH 2/3] btrfs: check/original: reject bad metadata backref with " Qu Wenruo
2022-01-17 2:48 ` Su Yue
2022-02-01 17:34 ` David Sterba
2022-01-17 2:38 ` [PATCH 3/3] btrfs-progs: tests/fsck: add test image with invalid metadata backref level Qu Wenruo
2022-02-01 17:37 ` [PATCH 0/3] btrfs-progs: fsck: detect obviously " David Sterba
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5yqjw00x.fsf@damenly.su \
--to=l@damenly.su \
--cc=linux-btrfs@vger.kernel.org \
--cc=wqu@suse.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).