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Mon, 29 Sep 2025 01:11:18 -0700 (PDT) Received: from localhost.localdomain ([111.92.125.119]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-27ed68821f8sm120319765ad.73.2025.09.29.01.11.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 Sep 2025 01:11:18 -0700 (PDT) From: Abinash Singh To: kent.overstreet@linux.dev Cc: linux-bcachefs@vger.kernel.org, linux-kernel@vger.kernel.org, Abinash Singh , syzbot+7fb23a5461e8c9d38a3e@syzkaller.appspotmail.com Subject: [PATCH RFC] bcachefs: Fix KMSAN uninit-value in __bch2_read_endio Date: Mon, 29 Sep 2025 13:41:10 +0530 Message-ID: <20250929081110.11618-1-abinashsinghlalotra@gmail.com> X-Mailer: git-send-email 2.43.0 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 reported a use of uninitialized memory in __bch2_read_endio(): BUG: KMSAN: uninit-value in __bch2_read_endio+0xb2a/0x2240 fs/bcachefs/io_read.c:832 ... Uninit was stored to memory at: poly1305_core_emit+0x46a/0x480 lib/crypto/poly1305-donna64.c:183 ... __bch2_checksum_bio+0x1048/0x1130 fs/bcachefs/checksum.c:237 The local `digest` buffer in __bch2_checksum_bio() was left uninitialized before being passed into Poly1305 routines, which caused KMSAN to flag it as an uninitialized read. Fix this by explicitly zero-initializing `digest`. Reported-by: syzbot+7fb23a5461e8c9d38a3e@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D7fb23a5461e8c9d38a3e Fixes: 1c6fdbd8f246 ("bcachefs: Initial commit") Signed-off-by: Abinash Singh --- fs/bcachefs/checksum.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/bcachefs/checksum.c b/fs/bcachefs/checksum.c index a6795e73f0b9..433ded62c77a 100644 --- a/fs/bcachefs/checksum.c +++ b/fs/bcachefs/checksum.c @@ -216,7 +216,7 @@ static struct bch_csum __bch2_checksum_bio(struct bch_f= s *c, unsigned type, case BCH_CSUM_chacha20_poly1305_80: case BCH_CSUM_chacha20_poly1305_128: { struct poly1305_desc_ctx dctx; - u8 digest[POLY1305_DIGEST_SIZE]; + u8 digest[POLY1305_DIGEST_SIZE] =3D { 0 }; struct bch_csum ret =3D { 0 }; =20 bch2_poly1305_init(&dctx, c, nonce); --=20 2.43.0