linux-kernel - Re: [PATCH v3 4/4] ext4: fix bug_on in __es_tree

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Date:   Wed, 26 Oct 2022 22:05:46 +0800
From:   Jason Yan <yanaijie@...wei.com>
To:     Baokun Li <libaokun1@...wei.com>, <linux-ext4@...r.kernel.org>
CC:     <tytso@....edu>, <adilger.kernel@...ger.ca>, <jack@...e.cz>,
        <ritesh.list@...il.com>, <linux-kernel@...r.kernel.org>,
        <yi.zhang@...wei.com>, <yukuai3@...wei.com>
Subject: Re: [PATCH v3 4/4] ext4: fix bug_on in __es_tree_search caused by bad
 boot loader inode


On 2022/10/26 12:23, Baokun Li wrote:
> We got a issue as fllows:
> ==================================================================
>   kernel BUG at fs/ext4/extents_status.c:203!
>   invalid opcode: 0000 [#1] PREEMPT SMP
>   CPU: 1 PID: 945 Comm: cat Not tainted 6.0.0-next-20221007-dirty #349
>   RIP: 0010:ext4_es_end.isra.0+0x34/0x42
>   RSP: 0018:ffffc9000143b768 EFLAGS: 00010203
>   RAX: 0000000000000000 RBX: ffff8881769cd0b8 RCX: 0000000000000000
>   RDX: 0000000000000000 RSI: ffffffff8fc27cf7 RDI: 00000000ffffffff
>   RBP: ffff8881769cd0bc R08: 0000000000000000 R09: ffffc9000143b5f8
>   R10: 0000000000000001 R11: 0000000000000001 R12: ffff8881769cd0a0
>   R13: ffff8881768e5668 R14: 00000000768e52f0 R15: 0000000000000000
>   FS: 00007f359f7f05c0(0000)GS:ffff88842fd00000(0000)knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 00007f359f5a2000 CR3: 000000017130c000 CR4: 00000000000006e0
>   DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>   DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>   Call Trace:
>    <TASK>
>    __es_tree_search.isra.0+0x6d/0xf5
>    ext4_es_cache_extent+0xfa/0x230
>    ext4_cache_extents+0xd2/0x110
>    ext4_find_extent+0x5d5/0x8c0
>    ext4_ext_map_blocks+0x9c/0x1d30
>    ext4_map_blocks+0x431/0xa50
>    ext4_mpage_readpages+0x48e/0xe40
>    ext4_readahead+0x47/0x50
>    read_pages+0x82/0x530
>    page_cache_ra_unbounded+0x199/0x2a0
>    do_page_cache_ra+0x47/0x70
>    page_cache_ra_order+0x242/0x400
>    ondemand_readahead+0x1e8/0x4b0
>    page_cache_sync_ra+0xf4/0x110
>    filemap_get_pages+0x131/0xb20
>    filemap_read+0xda/0x4b0
>    generic_file_read_iter+0x13a/0x250
>    ext4_file_read_iter+0x59/0x1d0
>    vfs_read+0x28f/0x460
>    ksys_read+0x73/0x160
>    __x64_sys_read+0x1e/0x30
>    do_syscall_64+0x35/0x80
>    entry_SYSCALL_64_after_hwframe+0x63/0xcd
>    </TASK>
> ==================================================================
> 
> In the above issue, ioctl invokes the swap_inode_boot_loader function to
> swap inode<5> and inode<12>. However, inode<5> contain incorrect imode and
> disordered extents, and i_nlink is set to 1. The extents check for inode in
> the ext4_iget function can be bypassed bacause 5 is EXT4_BOOT_LOADER_INO.
> While links_count is set to 1, the extents are not initialized in
> swap_inode_boot_loader. After the ioctl command is executed successfully,
> the extents are swapped to inode<12>, in this case, run the `cat` command
> to view inode<12>. And Bug_ON is triggered due to the incorrect extents.
> 
> When the boot loader inode is not initialized, its imode can be one of the
> following:
> 1) the imode is a bad type, which is marked as bad_inode in ext4_iget and
>     set to S_IFREG.
> 2) the imode is good type but not S_IFREG.
> 3) the imode is S_IFREG.
> 
> The BUG_ON may be triggered by bypassing the check in cases 1 and 2.
> Therefore, when the boot loader inode is bad_inode or its imode is not
> S_IFREG, initialize the inode to avoid triggering the BUG.
> 
> Signed-off-by: Baokun Li <libaokun1@...wei.com>
> ---
>   fs/ext4/ioctl.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

Looks good,
Reviewed-by: Jason Yan <yanaijie@...wei.com>