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Fri, 17 Apr 2026 15:28:43 -0700 (PDT) Received: from li-4c4c4544-0032-4210-804c-c3c04f423534.ibm.com ([2600:1700:6476:1430::29]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-65314ea3ee2sm1338811d50.16.2026.04.17.15.28.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Apr 2026 15:28:43 -0700 (PDT) Message-ID: Subject: Re: [PATCH] hfsplus: zero-initialize data buffer in hfs_bnode_read_u16 and hfs_bnode_read_u8 From: Viacheslav Dubeyko To: Tristan Madani , Andrew Morton Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+217eb327242d08197efb@syzkaller.appspotmail.com, stable@vger.kernel.org, Tristan Madani , Viacheslav Dubeyko Date: Fri, 17 Apr 2026 15:28:41 -0700 In-Reply-To: <20260417193913.338982-1-tristan@talencesecurity.com> References: <20260417193913.338982-1-tristan@talencesecurity.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-1.fc43app2) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2026-04-17 at 19:39 +0000, Tristan Madani wrote: > hfs_bnode_read_u16() and hfs_bnode_read_u8() declare local data > variables without initialization, then pass them to hfs_bnode_read(). >=20 > When hfs_bnode_read() returns early due to an invalid offset on a > corrupted HFS+ image (the is_bnode_offset_valid() check), the data > buffer is never written and the functions return uninitialized stack > data. KMSAN flags this as a use of uninitialized memory. >=20 > Zero-initialize both data variables so that an early return from > hfs_bnode_read() produces a deterministic zero value instead of > stack garbage. >=20 > Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=3D217eb327242d08197efb > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Cc: stable@vger.kernel.org > Signed-off-by: Tristan Madani > --- > fs/hfsplus/bnode.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) >=20 > diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c > index 14f4995588ff..4404cd35c192 100644 > --- a/fs/hfsplus/bnode.c > +++ b/fs/hfsplus/bnode.c > @@ -96,7 +96,7 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, = int off, int len) > =20 > u16 hfs_bnode_read_u16(struct hfs_bnode *node, int off) > { > - __be16 data; > + __be16 data =3D 0; > /* TODO: optimize later... */ > hfs_bnode_read(node, &data, off, 2); > return be16_to_cpu(data); > @@ -104,7 +104,7 @@ u16 hfs_bnode_read_u16(struct hfs_bnode *node, int of= f) > =20 > u8 hfs_bnode_read_u8(struct hfs_bnode *node, int off) > { > - u8 data; > + u8 data =3D 0; > /* TODO: optimize later... */ > hfs_bnode_read(node, &data, off, 1); > return data; Both methods hfs_bnode_read_u16() and hfs_bnode_read_u8() call the hfs_bnode_read(). And it is widely used method. We need to make initializat= ion at all places where hfs_bnode_read() is called. Oppositely, we can initiali= ze buffer in hfs_bnode_read() itself. Thanks, Slava.