linux-kernel - Re: [PATCH v5] f2fs: fix potential .flags overflow on 32bit architecture

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Date:   Mon, 23 Mar 2020 03:40:16 -0700
From:   Joe Perches <joe@...ches.com>
To:     Chao Yu <yuchao0@...wei.com>, jaegeuk@...nel.org
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH v5] f2fs: fix potential .flags overflow on 32bit
 architecture

On Mon, 2020-03-23 at 11:18 +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.
[]
> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
[]
> @@ -362,7 +362,7 @@ static int do_read_inode(struct inode *inode)
>  	fi->i_flags = le32_to_cpu(ri->i_flags);
>  	if (S_ISREG(inode->i_mode))
>  		fi->i_flags &= ~F2FS_PROJINHERIT_FL;
> -	fi->flags = 0;
> +	bitmap_zero(fi->flags, BITS_TO_LONGS(FI_MAX));

Sorry, I misled you here, this should be

	bitmap_zero(fi->flags, FI_MAX);