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Wed, 18 Mar 2026 16:15:45 -0700 (PDT) MIME-Version: 1.0 References: <20260316140122.339697-1-ljs@kernel.org> In-Reply-To: <20260316140122.339697-1-ljs@kernel.org> From: Nhat Pham Date: Wed, 18 Mar 2026 16:15:32 -0700 X-Gm-Features: AaiRm51Xhh8juYV2EAR_4SySHxXtpK-bjpt087uOj2N5eSLVxWKvWKMaK5JCmgQ Message-ID: Subject: Re: [PATCH mm-hotfixes] mm/zswap: add missing kunmap_local() To: "Lorenzo Stoakes (Oracle)" Cc: Andrew Morton , Johannes Weiner , Yosry Ahmed , Chengming Zhou , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 005B41A0005 X-Rspamd-Server: rspam07 X-Stat-Signature: py9dsnzygownje5wp5w3p4xy6k6cyz5n X-Rspam-User: X-HE-Tag: 1773875746-503472 X-HE-Meta: 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 Q6EYTzOb 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 16, 2026 at 7:01=E2=80=AFAM 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 d= ue > 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@goog= le.com > Fixes: e2c3b6b21c77 ("mm: zswap: use SG list decompression APIs from zsma= lloc") > Signed-off-by: Lorenzo Stoakes (Oracle) Acked-by: Nhat Pham Thanks for the catch, Lorenzo :)