From: Boris Burkov <boris@bur.io>
To: fdmanana@kernel.org
Cc: linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 2/2] btrfs: fix iput() on error pointer after error during orphan cleanup
Date: Fri, 7 Jul 2023 13:26:43 -0700 [thread overview]
Message-ID: <20230707202643.GB2547493@zen> (raw)
In-Reply-To: <0acc9d8cea160460e4bf049d761d285697b925bf.1688403622.git.fdmanana@suse.com>
On Mon, Jul 03, 2023 at 06:15:31PM +0100, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
>
> At btrfs_orphan_cleanup(), if we can't find an inode (btrfs_iget() returns
> an -ENOENT error pointer), we proceed with 'ret' set to -ENOENT and the
> inode pointer set to ERR_PTR(-ENOENT). Later when we proceed to the body
> of the following if statement:
>
> if (ret == -ENOENT || inode->i_nlink) {
> (...)
> trans = btrfs_start_transaction(root, 1);
> if (IS_ERR(trans)) {
> ret = PTR_ERR(trans);
> iput(inode);
> goto out;
> }
> (...)
> ret = btrfs_del_orphan_item(trans, root,
> found_key.objectid);
> btrfs_end_transaction(trans);
> if (ret) {
> iput(inode);
> goto out;
> }
> continue;
> }
>
> If we get an error from btrfs_start_transaction() or from the call to
> btrfs_del_orphan_item() we end calling iput() against an inode pointer
> that has a value of ERR_PTR(-ENOENT), resulting in a crash with the
> following trace:
>
> [438876.667234] BUG: kernel NULL pointer dereference, address: 0000000000000096
> [438876.667456] #PF: supervisor read access in kernel mode
> [438876.667683] #PF: error_code(0x0000) - not-present page
> [438876.667868] PGD 0 P4D 0
> [438876.668050] Oops: 0000 [#1] PREEMPT SMP PTI
> [438876.668231] CPU: 0 PID: 2356187 Comm: mount Tainted: G W 6.4.0-rc6-btrfs-next-134+ #1
> [438876.668420] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014
> [438876.668617] RIP: 0010:iput+0xa/0x20
> [438876.668818] Code: ff ff ff 66 (...)
> [438876.669274] RSP: 0018:ffffafa9c0c9f9d0 EFLAGS: 00010282
> [438876.669512] RAX: ffffffffffffffe4 RBX: 000000000009453b RCX: 0000000000000000
> [438876.669746] RDX: 0000000000000001 RSI: ffffafa9c0c9f930 RDI: fffffffffffffffe
> [438876.669989] RBP: ffff95c612f3b800 R08: 0000000000000001 R09: ffffffffffffffe4
> [438876.670231] R10: 00018f2a71010000 R11: 000000000ead96e3 R12: ffff95cb7d6909a0
> [438876.670476] R13: fffffffffffffffe R14: ffff95c60f477000 R15: 00000000ffffffe4
> [438876.670730] FS: 00007f5fbe30a840(0000) GS:ffff95ccdfa00000(0000) knlGS:0000000000000000
> [438876.670999] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [438876.671296] CR2: 0000000000000096 CR3: 000000055e9f6004 CR4: 0000000000370ef0
> [438876.671648] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [438876.671984] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [438876.672264] Call Trace:
> [438876.744284] <TASK>
> [438876.744589] ? __die_body+0x1b/0x60
> [438876.744872] ? page_fault_oops+0x15d/0x450
> [438876.745170] ? __kmem_cache_alloc_node+0x47/0x410
> [438876.745459] ? do_user_addr_fault+0x65/0x8a0
> [438876.745740] ? exc_page_fault+0x74/0x170
> [438876.746021] ? asm_exc_page_fault+0x22/0x30
> [438876.746305] ? iput+0xa/0x20
> [438876.746586] btrfs_orphan_cleanup+0x221/0x330 [btrfs]
> [438876.746917] btrfs_lookup_dentry+0x58f/0x5f0 [btrfs]
> [438876.747251] btrfs_lookup+0xe/0x30 [btrfs]
> [438876.747564] __lookup_slow+0x82/0x130
> [438876.785817] walk_component+0xe5/0x160
> [438876.786129] path_lookupat.isra.0+0x6e/0x150
> [438876.786411] filename_lookup+0xcf/0x1a0
> [438876.786687] ? mod_objcg_state+0xd2/0x360
> [438876.786954] ? obj_cgroup_charge+0xf5/0x110
> [438876.787255] ? should_failslab+0xa/0x20
> [438876.787519] ? kmem_cache_alloc+0x47/0x450
> [438876.787772] vfs_path_lookup+0x51/0x90
> [438876.788023] mount_subtree+0x8d/0x130
> [438876.788306] btrfs_mount+0x149/0x410 [btrfs]
> [438876.788624] ? __kmem_cache_alloc_node+0x47/0x410
> [438876.788899] ? vfs_parse_fs_param+0xc0/0x110
> [438876.789175] legacy_get_tree+0x24/0x50
> [438876.834144] vfs_get_tree+0x22/0xd0
> [438876.852406] path_mount+0x2d8/0x9c0
> [438876.852684] do_mount+0x79/0x90
> [438876.852914] __x64_sys_mount+0x8e/0xd0
> [438876.853135] do_syscall_64+0x38/0x90
> [438876.899182] entry_SYSCALL_64_after_hwframe+0x72/0xdc
> [438876.958854] RIP: 0033:0x7f5fbe50b76a
> [438876.959113] Code: 48 8b 0d a9 (...)
> [438876.959578] RSP: 002b:00007fff01925798 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
> [438876.959808] RAX: ffffffffffffffda RBX: 00007f5fbe694264 RCX: 00007f5fbe50b76a
> [438876.960026] RDX: 0000561bde6c8720 RSI: 0000561bde6bdec0 RDI: 0000561bde6c31a0
> [438876.960238] RBP: 0000561bde6bdc70 R08: 0000000000000000 R09: 0000000000000001
> [438876.960448] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> [438876.960657] R13: 0000561bde6c31a0 R14: 0000561bde6c8720 R15: 0000561bde6bdc70
> [438876.960868] </TASK>
>
> So fix this by setting 'inode' to NULL whenever we get an error from
> btrfs_iget(), and to make the code simpler, stop testing for 'ret' being
> -ENOENT to check if we have an inode - instead test for 'inode' being NULL
> or not. Having a NULL 'inode' prevents any iput() call from crashing, as
> iput() ignores NULL inode pointers. Also, stop testing for a NULL return
> value from btrfs_iget() with PTR_ERR_OR_ZERO(), because btrfs_iget() never
> returns NULL - in case an inode is not found, it returns ERR_PTR(-ENOENT),
> and in case of memory allocation failure, it returns ERR_PTR(-ENOMEM).
> We also don't need the extra iput() calls on the error branches for the
> btrfs_start_transaction() and btrfs_del_orphan_item() calls, as we have
> already called iput() before, so remove them.
>
> Fixes: a13bb2c03848 ("btrfs: add missing iputs on orphan cleanup failure")
> Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Boris Burkov <boris@bur.io>
> ---
> fs/btrfs/inode.c | 20 ++++++++++----------
> 1 file changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index d919318d2498..c8921589e2f3 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -3659,11 +3659,14 @@ int btrfs_orphan_cleanup(struct btrfs_root *root)
> found_key.type = BTRFS_INODE_ITEM_KEY;
> found_key.offset = 0;
> inode = btrfs_iget(fs_info->sb, last_objectid, root);
> - ret = PTR_ERR_OR_ZERO(inode);
> - if (ret && ret != -ENOENT)
> - goto out;
> + if (IS_ERR(inode)) {
> + ret = PTR_ERR(inode);
> + inode = NULL;
> + if (ret != -ENOENT)
> + goto out;
> + }
>
> - if (ret == -ENOENT && root == fs_info->tree_root) {
> + if (!inode && root == fs_info->tree_root) {
> struct btrfs_root *dead_root;
> int is_dead_root = 0;
>
> @@ -3724,8 +3727,8 @@ int btrfs_orphan_cleanup(struct btrfs_root *root)
> * deleted but wasn't. The inode number may have been reused,
> * but either way, we can delete the orphan item.
> */
> - if (ret == -ENOENT || inode->i_nlink) {
> - if (!ret) {
> + if (!inode || inode->i_nlink) {
> + if (inode) {
> ret = btrfs_drop_verity_items(BTRFS_I(inode));
> iput(inode);
> inode = NULL;
> @@ -3735,7 +3738,6 @@ int btrfs_orphan_cleanup(struct btrfs_root *root)
> trans = btrfs_start_transaction(root, 1);
> if (IS_ERR(trans)) {
> ret = PTR_ERR(trans);
> - iput(inode);
> goto out;
> }
> btrfs_debug(fs_info, "auto deleting %Lu",
> @@ -3743,10 +3745,8 @@ int btrfs_orphan_cleanup(struct btrfs_root *root)
> ret = btrfs_del_orphan_item(trans, root,
> found_key.objectid);
> btrfs_end_transaction(trans);
> - if (ret) {
> - iput(inode);
> + if (ret)
> goto out;
> - }
> continue;
> }
>
> --
> 2.34.1
>
next prev parent reply other threads:[~2023-07-07 20:28 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-03 17:15 [PATCH 0/2] btrfs: fix error paths of btrfs_orphan_cleanup() fdmanana
2023-07-03 17:15 ` [PATCH 1/2] btrfs: fix double iput() on inode after an error during orphan cleanup fdmanana
2023-07-07 20:26 ` Boris Burkov
2023-07-03 17:15 ` [PATCH 2/2] btrfs: fix iput() on error pointer after " fdmanana
2023-07-07 20:26 ` Boris Burkov [this message]
2023-07-11 19:59 ` [PATCH 0/2] btrfs: fix error paths of btrfs_orphan_cleanup() 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=20230707202643.GB2547493@zen \
--to=boris@bur.io \
--cc=fdmanana@kernel.org \
--cc=linux-btrfs@vger.kernel.org \
/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