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Mon, 16 Mar 2026 08:17:33 -0700 (PDT) Date: Mon, 16 Mar 2026 11:17:32 -0400 From: Johannes Weiner To: "Lorenzo Stoakes (Oracle)" Cc: Andrew Morton , Yosry Ahmed , Nhat Pham , Chengming Zhou , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH mm-hotfixes] mm/zswap: add missing kunmap_local() Message-ID: References: <20260316140122.339697-1-ljs@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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) Oops! Acked-by: Johannes Weiner