linux-ext4 - Re: [PATCH 4/4] e2fsck: initialize variable before first use in fast commit replay

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Date:   Sun, 21 Feb 2021 18:14:06 -0500
From:   "Theodore Ts'o" <tytso@....edu>
To:     Harshad Shirwadkar <harshadshirwadkar@...il.com>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: [PATCH 4/4] e2fsck: initialize variable before first use in fast
 commit replay

On Fri, Feb 19, 2021 at 01:03:33PM -0800, Harshad Shirwadkar wrote:
> From: Harshad Shirwadkar <harshadshirwadkar@...il.com>
> 
> Initialize ext2fs_ex variable in ext4_fc_replay_scan() before first
> use.
> 
> Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@...il.com>

I wonder if we should make the following change to
ext2fs_decode_extent(), which will prevent other future bugs to
potential users of the function:

	to->e_pblk = ext2fs_le32_to_cpu(from->ee_start) +
		((__u64) ext2fs_le16_to_cpu(from->ee_start_hi)
			<< 32);
	to->e_lblk = ext2fs_le32_to_cpu(from->ee_block);
	to->e_len = ext2fs_le16_to_cpu(from->ee_len);
-	to->e_flags |= EXT2_EXTENT_FLAGS_LEAF;
+	to->e_flags = EXT2_EXTENT_FLAGS_LEAF;

ext2fs_decode_extent() overwrites all other members of the structure,
so we might as well just initialize e_flags as opposed to depending
the caller to initiaize *to just for the sake of to->e_flags.

Cheers,

					- Ted