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Date: Thu, 18 Dec 2025 13:21:16 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Matthew Wilcox <willy@infradead.org>, Andrii Nakryiko
 <andrii@kernel.org>, Shaurya Rane <ssrane_b23@ee.vjti.ac.in>,
 "Darrick J . Wong" <djwong@kernel.org>, Christoph Hellwig
 <hch@infradead.org>, Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann
 <daniel@iogearbox.net>, Meta kernel team <kernel-team@meta.com>,
 bpf@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
 linux-kernel@vger.kernel.org,
 syzbot+09b7d050e4806540153d@syzkaller.appspotmail.com, Christoph Hellwig
 <hch@lst.de>
Subject: Re: [PATCH bpf v2] lib/buildid: use __kernel_read() for sleepable
 context
Message-Id: <20251218132116.c1edb3ee6688605bd270a666@linux-foundation.org>
In-Reply-To: <20251218205505.2415840-1-shakeel.butt@linux.dev>
References: <20251218205505.2415840-1-shakeel.butt@linux.dev>
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On Thu, 18 Dec 2025 12:55:05 -0800 Shakeel Butt <shakeel.butt@linux.dev> wrote:

> For the sleepable context, convert freader to use __kernel_read()
> instead of direct page cache access via read_cache_folio(). This
> simplifies the faultable code path by using the standard kernel file
> reading interface which handles all the complexity of reading file data.
> 
> At the moment we are not changing the code for non-sleepable context
> which uses filemap_get_folio() and only succeeds if the target folios
> are already in memory and up-to-date. The reason is to keep the patch
> simple and easier to backport to stable kernels.
> 
> Syzbot repro does not crash the kernel anymore and the selftests run
> successfully.
> 
> In the follow up we will make __kernel_read() with IOCB_NOWAIT work for
> non-sleepable contexts. In addition, I would like to replace the
> secretmem check with a more generic approach and will add fstest for the
> buildid code.
> 
> Reported-by: syzbot+09b7d050e4806540153d@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=09b7d050e4806540153d
> Fixes: ad41251c290d ("lib/buildid: implement sleepable build_id_parse() API")

v6.12.

> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>

Thanks, I'll add cc:stable to this due to "crashes the kernel".