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From: Chao Yu <chao@kernel.org>
To: Gao Xiang <hsiangkao@linux.alibaba.com>, linux-erofs@lists.ozlabs.org
Cc: chao@kernel.org, LKML <linux-kernel@vger.kernel.org>,
	syzbot+1a9af3ef3c84c5e14dcc@syzkaller.appspotmail.com
Subject: Re: [PATCH] erofs: avoid reading more for fragment maps
Date: Tue, 23 Sep 2025 10:21:05 +0800	[thread overview]
Message-ID: <338fd84f-80fd-4ec7-b87e-64e76015b8f4@kernel.org> (raw)
In-Reply-To: <20250916084851.1759111-1-hsiangkao@linux.alibaba.com>

On 9/16/25 16:48, Gao Xiang wrote:
> Since all real encoded extents (directly handled by the decompression
> subsystem) have a sane, limited maximum decoded length
> (Z_EROFS_PCLUSTER_MAX_DSIZE), and the read‑more policy is only applied
> if needed.
> 
> However, it makes no sense to read more for non‑encoded maps, such as
> fragment extents, since such extents can be huge (up to i_size) and
> there is no benefit to reading more at this layer.
> 
> For normal images, it does not really matter, but for crafted images
> generated by syzbot, excessively large fragment extents can cause
> read‑more to run for an overly long time.
> 
> Reported-by: syzbot+1a9af3ef3c84c5e14dcc@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/r/68c8583d.050a0220.2ff435.03a3.GAE@google.com
> Fixes: b44686c8391b ("erofs: fix large fragment handling")
> Fixes: b15b2e307c3a ("erofs: support on-disk compressed fragments data")
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,


  parent reply	other threads:[~2025-09-23  2:21 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-09-15 18:17 [syzbot] [erofs?] INFO: task hung in erofs_bread syzbot
2025-09-16  8:48 ` [PATCH] erofs: avoid reading more for fragment maps Gao Xiang
2025-09-16 13:23   ` Hongbo Li
2025-09-23  2:21   ` Chao Yu [this message]
2025-09-16  9:01 ` [syzbot] [erofs?] INFO: task hung in erofs_bread Gao Xiang
2025-09-16  9:30   ` syzbot

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