From: Johannes Weiner <hannes@cmpxchg.org>
To: "Lorenzo Stoakes (Oracle)" <ljs@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Yosry Ahmed <yosry@kernel.org>, Nhat Pham <nphamcs@gmail.com>,
Chengming Zhou <chengming.zhou@linux.dev>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH mm-hotfixes] mm/zswap: add missing kunmap_local()
Date: Mon, 16 Mar 2026 11:17:32 -0400 [thread overview]
Message-ID: <abgfDB-6RDjTar1d@cmpxchg.org> (raw)
In-Reply-To: <20260316140122.339697-1-ljs@kernel.org>
On Mon, Mar 16, 2026 at 02:01:22PM +0000, Lorenzo Stoakes (Oracle) wrote:
> Commit e2c3b6b21c77 ("mm: zswap: use SG list decompression APIs from
> zsmalloc") updated zswap_decompress() to use the scatterwalk API to copy
> data for uncompressed pages.
>
> In doing so, it mapped kernel memory locally for 32-bit kernels using
> kmap_local_folio(), however it never unmapped this memory.
>
> This resulted in the linked syzbot report where a BUG_ON() is triggered due
> to leaking the kmap slot.
>
> This patch fixes the issue by explicitly unmapping the established kmap.
>
> Reported-by: syzbot+fe426bef95363177631d@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/all/69b75e2c.050a0220.12d28.015a.GAE@google.com
> Fixes: e2c3b6b21c77 ("mm: zswap: use SG list decompression APIs from zsmalloc")
> Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Oops!
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
next prev parent reply other threads:[~2026-03-16 15:17 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-16 14:01 [PATCH mm-hotfixes] mm/zswap: add missing kunmap_local() Lorenzo Stoakes (Oracle)
2026-03-16 14:52 ` Yosry Ahmed
2026-03-16 15:49 ` Lorenzo Stoakes (Oracle)
2026-03-16 15:17 ` Johannes Weiner [this message]
2026-03-17 0:38 ` SeongJae Park
2026-03-17 10:01 ` Lorenzo Stoakes (Oracle)
2026-03-17 12:13 ` Lorenzo Stoakes (Oracle)
2026-03-17 12:59 ` Lorenzo Stoakes (Oracle)
2026-03-17 18:01 ` Andrew Morton
2026-03-17 19:01 ` Yosry Ahmed
2026-03-18 0:34 ` SeongJae Park
2026-03-18 23:15 ` Nhat Pham
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