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Thu, 19 Feb 2026 02:18:40 -0800 (PST) From: Abd-Alrhman Masalkhi To: Thomas =?utf-8?Q?Wei=C3=9Fschuh?= Cc: dwlsalmeida@gmail.com, mchehab@kernel.org, linmag7@gmail.com, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+96f901260a0b2d29cd1a@syzkaller.appspotmail.com Subject: Re: [PATCH] media: vidtv: fix uninitialized args.buf_sz passed by value In-Reply-To: <20260218141123-d54e3a23-c3dc-4ce7-8a8f-1d77fa4c7960@linutronix.de> References: <20260216211703.3702-1-abd.masalkhi@gmail.com> <20260218141123-d54e3a23-c3dc-4ce7-8a8f-1d77fa4c7960@linutronix.de> Date: Thu, 19 Feb 2026 11:17:55 +0100 Message-ID: Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Wed, Feb 18, 2026 at 14:24 +0100, Thomas Wei=C3=9Fschuh wrote: Hi Thomas, Thank you for the feedback. > Hi Abd-Alrhman! > > On Mon, Feb 16, 2026 at 10:17:03PM +0100, Abd-Alrhman Masalkhi wrote: >> vidtv_ts_null_write_into() takes null_packet_write_args by value, >> causing MSAN to report an uninit-value warning on buf_sz inside >> the function. >>=20 >> Fix by passing the struct by pointer instead, avoiding the stack copy >> entirely. >>=20 >> Reported-by: syzbot+96f901260a0b2d29cd1a@syzkaller.appspotmail.com >> Closes: https://syzkaller.appspot.com/bug?extid=3D96f901260a0b2d29cd1a >> Fixes: cd7a5651db26 ("alpha: add missing address argument in call to pag= e_table_check_pte_clear()") > > The Fixes tag should point to the commit which originally introduced > the issue that is being fixed. My commit for alpha-specific code is > unlikely to be the root cause because a) syscaller is not running alpha > systems and b) the first occurrence of the syscaller was before my patch > was picked up by Linus. So please try to find a better Fixes tag. > I will fix the Fixes tag to point to the correct vidtv commit. >> Signed-off-by: Abd-Alrhman Masalkhi >> --- >> drivers/media/test-drivers/vidtv/vidtv_mux.c | 2 +- >> drivers/media/test-drivers/vidtv/vidtv_ts.c | 18 +++++++++--------- >> drivers/media/test-drivers/vidtv/vidtv_ts.h | 2 +- >> 3 files changed, 11 insertions(+), 11 deletions(-) >>=20 >> diff --git a/drivers/media/test-drivers/vidtv/vidtv_mux.c b/drivers/medi= a/test-drivers/vidtv/vidtv_mux.c >> index f99878eff7ac..67a580396112 100644 >> --- a/drivers/media/test-drivers/vidtv/vidtv_mux.c >> +++ b/drivers/media/test-drivers/vidtv/vidtv_mux.c >> @@ -363,7 +363,7 @@ static u32 vidtv_mux_pad_with_nulls(struct vidtv_mux= *m, u32 npkts) >> args.continuity_counter =3D &ctx->cc; >>=20=20 >> for (i =3D 0; i < npkts; ++i) { >> - m->mux_buf_offset +=3D vidtv_ts_null_write_into(args); >> + m->mux_buf_offset +=3D vidtv_ts_null_write_into(&args); > > Please explain in the commit message why this is change is safe to do. > Modifying shared data might break the logic. (I have not verified this) > vidtv_ts_null_write_into() only reads from the struct and does not modify it. should I add a const qualifier to the parameter?=20 >> args.dest_offset =3D m->mux_buf_offset; >> } > > (...) > > Did have syscaller test this patch before submission? > See the following documentation from the report: > > If you want syzbot to run the reproducer, reply with: > #syz test: git://repo/address.git branch-or-commit-hash > If you attach or paste a git patch, syzbot will apply it before testing. > I will test with syzbot before sending v2. > > Thomas --=20 Best Regards, Abd-Alrhman