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Mon, 04 May 2026 16:29:33 -0700 (PDT) Received: from li-4c4c4544-0032-4210-804c-c3c04f423534.ibm.com ([2600:1700:6476:1430::29]) by smtp.gmail.com with ESMTPSA id 00721157ae682-7bd7d849afesm37183217b3.49.2026.05.04.16.29.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 May 2026 16:29:33 -0700 (PDT) Message-ID: Subject: Re: [PATCH 2/3] hfs/hfsplus: initialize data buffer in hfs_bnode_read_u16 and hfs_bnode_read_u8 From: Viacheslav Dubeyko To: Tristan Madani , Viacheslav Dubeyko , John Paul Adrian Glaubitz , Yangtao Li Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Tristan Madani , syzbot+217eb327242d08197efb@syzkaller.appspotmail.com Date: Mon, 04 May 2026 16:29:31 -0700 In-Reply-To: <20260501110218.29906-2-tristmd@gmail.com> References: <20260501110218.29906-1-tristmd@gmail.com> <20260501110218.29906-2-tristmd@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.0 (3.60.0-1.fc44app2) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2026-05-01 at 11:02 +0000, Tristan Madani wrote: > From: Tristan Madani >=20 > hfs_bnode_read_u16() and hfs_bnode_read_u8() declare local data buffers > without initialization, then pass them to hfs_bnode_read(). If > is_bnode_offset_valid() fails inside hfs_bnode_read(), the function > returns early without writing to the buffer, leaving it uninitialized. > The caller then returns the garbage value to its caller. >=20 > This triggers KMSAN uninit-value reports when a corrupted HFS+ image > has a node_size of 1, causing rec_off to underflow in hfs_bnode_find() > and the subsequent hfs_bnode_read_u16() to operate on an invalid offset. >=20 > Zero-initialize both buffers so that callers get a deterministic zero > value when the underlying read fails. >=20 > Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=3D217eb327242d08197efb > Tested-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com > Fixes: a431930c9bac ("hfs: fix slab-out-of-bounds in hfs_bnode_read()") > Cc: stable@vger.kernel.org > Signed-off-by: Tristan Madani > --- > fs/hfs/bnode.c | 4 ++-- > fs/hfsplus/bnode.c | 4 ++-- > 2 files changed, 4 insertions(+), 4 deletions(-) >=20 > diff --git a/fs/hfs/bnode.c b/fs/hfs/bnode.c > index c00645a4a5733..08307faea7a68 100644 > --- a/fs/hfs/bnode.c > +++ b/fs/hfs/bnode.c > @@ -97,7 +97,7 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, = u32 off, u32 len) > =20 > u16 hfs_bnode_read_u16(struct hfs_bnode *node, u32 off) > { > - __be16 data; > + __be16 data =3D 0; > // optimize later... > hfs_bnode_read(node, &data, off, 2); > return be16_to_cpu(data); > @@ -105,7 +105,7 @@ u16 hfs_bnode_read_u16(struct hfs_bnode *node, u32 of= f) > =20 > u8 hfs_bnode_read_u8(struct hfs_bnode *node, u32 off) > { > - u8 data; > + u8 data =3D 0; > // optimize later... > hfs_bnode_read(node, &data, off, 1); > return data; > diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c > index f8b5a8ae58ff5..35790085b5b2e 100644 > --- a/fs/hfsplus/bnode.c > +++ b/fs/hfsplus/bnode.c > @@ -55,7 +55,7 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, = u32 off, u32 len) > =20 > u16 hfs_bnode_read_u16(struct hfs_bnode *node, u32 off) > { > - __be16 data; > + __be16 data =3D 0; > /* TODO: optimize later... */ > hfs_bnode_read(node, &data, off, 2); > return be16_to_cpu(data); > @@ -63,7 +63,7 @@ u16 hfs_bnode_read_u16(struct hfs_bnode *node, u32 off) > =20 > u8 hfs_bnode_read_u8(struct hfs_bnode *node, u32 off) > { > - u8 data; > + u8 data =3D 0; > /* TODO: optimize later... */ > hfs_bnode_read(node, &data, off, 1); > return data; If I remember correctly, I already shared that hfs_bnode_read() is called i= n multiple places. So, this patch is not enough for complete fix of the issue= . Thanks, Slava.