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[195.20.212.194]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b8037ad1e6dsm1559098366b.21.2025.12.23.13.59.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Dec 2025 13:59:11 -0800 (PST) From: Bartlomiej Kubik To: tytso@mit.edu Cc: adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, david.hunter.linux@gmail.com, skhan@linuxfoundation.org, khalid@kernel.org, linux-kernel-mentees@lists.linux.dev, Bartlomiej Kubik , syzbot+703d8a2cd20971854b06@syzkaller.appspotmail.com Subject: [PATCH] fs/ext4: Initialize new folios before use Date: Tue, 23 Dec 2025 22:58:55 +0100 Message-Id: <20251223215855.2486271-1-kubik.bartlomiej@gmail.com> X-Mailer: git-send-email 2.39.5 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" KMSAN reports an uninitialized value in adiantum_crypt, created at write_begin_get_folio(). New folios are allocated with the FGP_CREAT flag and may be returned uninitialized. These uninitialized folios are then used without proper initialization. Fixes: b799474b9aeb ("mm/pagemap: add write_begin_get_folio() helper functi= on") Tested-by: syzbot+703d8a2cd20971854b06@syzkaller.appspotmail.com Reported-by: syzbot+703d8a2cd20971854b06@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D703d8a2cd20971854b06 Signed-off-by: Bartlomiej Kubik --- include/linux/pagemap.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 31a848485ad9..31bbc8299e08 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -787,7 +787,8 @@ static inline struct folio *write_begin_get_folio(const= struct kiocb *iocb, fgp_flags |=3D FGP_DONTCACHE; return __filemap_get_folio(mapping, index, fgp_flags, - mapping_gfp_mask(mapping)); + mapping_gfp_mask(mapping)| + __GFP_ZERO); } /** -- 2.39.5