linux-kernel - Re: [PATCH v4] f2fs: fix potential .flags overflow on 32bit architecture

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Date:   Mon, 23 Mar 2020 04:05:49 +0100
From:   Ondřej Jirman <megi@....cz>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     jaegeuk@...nel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH v4] f2fs: fix potential .flags overflow on 32bit
 architecture

Hello,

On Mon, Mar 23, 2020 at 10:41:09AM +0800, Chao Yu wrote:
> f2fs_inode_info.flags is unsigned long variable, it has 32 bits
> in 32bit architecture, since we introduced FI_MMAP_FILE flag
> when we support data compression, we may access memory cross
> the border of .flags field, corrupting .i_sem field, result in
> below deadlock.
> 
> To fix this issue, let's expand .flags as an array to grab enough
> space to store new flags.
> 
> Call Trace:
>  __schedule+0x8d0/0x13fc
>  ? mark_held_locks+0xac/0x100
>  schedule+0xcc/0x260
>  rwsem_down_write_slowpath+0x3ab/0x65d
>  down_write+0xc7/0xe0
>  f2fs_drop_nlink+0x3d/0x600 [f2fs]
>  f2fs_delete_inline_entry+0x300/0x440 [f2fs]
>  f2fs_delete_entry+0x3a1/0x7f0 [f2fs]
>  f2fs_unlink+0x500/0x790 [f2fs]
>  vfs_unlink+0x211/0x490
>  do_unlinkat+0x483/0x520
>  sys_unlink+0x4a/0x70
>  do_fast_syscall_32+0x12b/0x683
>  entry_SYSENTER_32+0xaa/0x102
> 
> Fixes: 4c8ff7095bef ("f2fs: support data compression")
> Signed-off-by: Chao Yu <yuchao0@...wei.com>

Tested-by: Ondrej Jirman <megous@...ous.com>

This patch alone also fixes all the other lockups I reported recently,
that were easier to trigger than this one.

thanks,
	o.