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Sat, 5 Sep 2026 02:22:11 +0200 (CEST) Message-ID: <1b247f730001ea39b6e4044f5673e1a01e187362.camel@posteo.de> Subject: Re: [PATCH] rust: serdev: Fix race condition on driver probe fail From: Markus Probst To: Miguel Ojeda , Boqun Feng , Gary Guo , =?ISO-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , Onur =?ISO-8859-1?Q?=D6zkan?= , Greg Kroah-Hartman Cc: linux-serial@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Sashiko Bot Date: Sat, 05 Sep 2026 00:22:12 +0000 In-Reply-To: <20260905-rust_serdev_fix-v1-1-2ea92b154a6b@posteo.de> References: <20260905-rust_serdev_fix-v1-1-2ea92b154a6b@posteo.de> Autocrypt: addr=markus.probst@posteo.de; prefer-encrypt=mutual; keydata=mQINBGiDvXgBEADAXUceKafpl46S35UmDh2wRvvx+UfZbcTjeQOlSwKP7YVJ4JOZrVs93 qReNLkOWguIqPBxR9blQ4nyYrqSCV+MMw/3ifyXIm6Pw2YRUDg+WTEOjTixRCoWDgUj1nOsvJ9tVA m76Ww+/pAnepVRafMID0rqEfD9oGv1YrfpeFJhyE2zUw3SyyNLIKWD6QeLRhKQRbSnsXhGLFBXCqt 9k5JARhgQof9zvztcCVlT5KVvuyfC4H+HzeGmu9201BVyihJwKdcKPq+n/aY5FUVxNTgtI9f8wIbm fAjaoT1pjXSp+dszakA98fhONM98pOq723o/1ZGMZukyXFfsDGtA3BB79HoopHKujLGWAGskzClwT jRQxBqxh/U/lL1pc+0xPWikTNCmtziCOvv0KA0arDOMQlyFvImzX6oGVgE4ksKQYbMZ3Ikw6L1Rv1 J+FvN0aNwOKgL2ztBRYscUGcQvA0Zo1fGCAn/BLEJvQYShWKeKqjyncVGoXFsz2AcuFKe1pwETSsN 6OZncjy32e4ktgs07cWBfx0v62b8md36jau+B6RVnnodaA8++oXl3FRwiEW8XfXWIjy4umIv93tb8 8ekYsfOfWkTSewZYXGoqe4RtK80ulMHb/dh2FZQIFyRdN4HOmB4FYO5sEYFr9YjHLmDkrUgNodJCX CeMe4BO4iaxUQARAQABtCdNYXJrdXMgUHJvYnN0IDxtYXJrdXMucHJvYnN0QHBvc3Rlby5kZT6JAl QEEwEIAD4CGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AWIQSCdBjE9KxY53IwxHM0dh/4561 D0gUCaIZ9HQIZAQAKCRA0dh/4561D0pKmD/92zsCfbD+SrvBpNWtbit7J9wFBNr9qSFFm2n/65qen NNWKDrCzDsjRbALMHSO8nigMWzjofbVjj8Nf7SDcdapRjrMCnidS0DuW3pZBo6W0sZqV/fLx+AzgQ 7PAr6jtBbUoKW/GCGHLLtb6Hv+zjL17KGVO0DdQeoHEXMa48mJh8rS7VlUzVtpbxsWbb1wRZJTD88 ALDOLTWGqMbCTFDKFfGcqBLdUT13vx706Q29wrDiogmQhLGYKc6fQzpHhCLNhHTl8ZVLuKVY3wTT+ f9TzW1BDzFTAe3ZXsKhrzF+ud7vr6ff9p1Zl+Nujz94EDYHi/5Yrtp//+N/ZjDGDmqZOEA86/Gybu 6XE/v4S85ls0cAe37WTqsMCJjVRMP52r7Y1AuOONJDe3sIsDge++XFhwfGPbZwBnwd4gEVcdrKhnO ntuP9TvBMFWeTvtLqlWJUt7n8f/ELCcGoO5acai1iZ59GC81GLl2izObOLNjyv3G6hia/w50Mw9MU dAdZQ2MxM6k+x4L5XeysdcR/2AydVLtu2LGFOrKyEe0M9XmlE6OvziWXvVVwomvTN3LaNUmaINhr7 pHTFwDiZCSWKnwnvD2+jA1trKq1xKUQY1uGW9XgSj98pKyixHWoeEpydr+alSTB43c3m0351/9rYT TTi4KSk73wtapPKtaoIR3rOFHLQXbWFya3VzLnByb2JzdEBwb3N0ZW8uZGWJAlEEEwEIADsWIQSCd BjE9KxY53IwxHM0dh/4561D0gUCaIO9eAIbAwULCQgHAgIiAgYVCgkICwIEFgIDAQIeBwIXgAAKCR A0dh/4561D0oHZEACEmk5Ng9+OXoVxJJ+c9slBI2lYxyBO84qkWjoJ/0GpwoHk1IpyL+i+kF1Bb7y Hx9Tiz8ENYX7xIPTZzS8hXs1ksuo76FQUyD6onA/69xZIrYZ0NSA5HUo62qzzMSZL7od5e12R6OPR lR0PIuc4ecOGCEq3BLRPfZSYrL54tiase8HubXsvb6EBQ8jPI8ZUlr96ZqFEwrQZF/3ihyV6LILLk geExgwlTzo5Wv3piOXPTITBuzuFhBJqEnT25q2j8OumGQ+ri8oVeAzx24g1kc11pwpR0sowfa5MvZ WrrBcaIL7uJfR/ig7FyGnTQ1nS3btf3p0v8A3fc4eUu/K2No3l2huJp3+LHhCmpmeykOhSB63Mj3s 3Q87LD0HE0HBkTEMwp+sD97ZRpO67H5shzJRanUaDTb/mREfzpJmRT1uuec0X2zItL7a6itgMJvYI KG29aJLX3fTzzVzFGPgzVZYEdhu4y53p0qEGrrC1JtKR6DRPE1hb/OdWOkjmJ75+PPLD9U5IuRd6y sHJWsEBR1F0wkMPkEofWsvMYJzWXx/rvTWO8N4D6HigTgBXAXNgbc3IHpHlkvKoBJptv6DRVRtIrz 0G0cfBY0Sm7he4N2IYDWWdGnPBZ3rlLSdj5EiBU2YWgIgtLrb8ZNJ3ZlhYluGnBJDGRqy2jC9s1jY 66sLA9rQZMHhJTzMyIDwweGlvMzJAcG9zdGVvLmV1PokCbQQTAQgAVxYhBIJ0GMT0rFjncjDEczR2 H/jnrUPSBQJpa71VGxSAAAAAAAQADm1hbnUyLDIuNSsxLjExLDIsMgIbAwULCQgHAgIiAgYVCgkIC wIEFgIDAQIeBwIXgAAKCRA0dh/4561D0gKJD/9uOQKYlsDoQX65Gd0LiMT0C+5vXgr3VI0PHDOwcv 51fJ3A1vNyPZRFPGrz8+mDEXUQOF/INfnz5Tu1QHwf+iYcWcTGAN/FHgVR6ET6VBNU2hJaKhu+Ggo kjYyJTOvyX+3yNRUfSny0GjTjIPuPTErjqmHF+BtjXslpgwqnNMznf3lRIuUjRORupos6p3k1DndE 5vzUTmXSvMyXyOD2KhBl/kL76k0bHYyAQytZPag12pltrtFbA/r2phDGN2si8PooDT99bSTJjaM45 MTAAHbHKJfvgfK41bNFD5mMtpWpL195XRtS0Nrxdg3PaYBxN5gtTG0RyZfpYRlkdEhm+jj/8RxuSG i/qdhRdbiI7K2IELWeQVHSNDi9JabR/UzlR4NSnhfAjRIVlRM+eFbUl8XwxwVrAkojF5IraH2qRvg VCmuFsHUW07FUlrDrzpjXsD73cKppoFGDCdDR0BHJepXbFLS9+AqkT+guRJlnCTg2p+TQtnbwPgKp Vj98JixovCl99zRYTsL2bRNU5+q8iET65VMJ1ydyNanvLd5vI/NqDkXhlXLsGmdaDTtu4R21PkToX dQNGrZ91M9nlIBKw8Y7c7xZ4098qX2b8JX/CxD+gC1r4C8vuA3GkhFLx+KlkON7LyiJPkrePp6Qky jfGillcaQOqFZ3WwVqyzG1BUfTow== Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-ba5r6Ds701NYq8n4AnLV" Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 OpenPGP: url=https://posteo.de/keys/markus.probst@posteo.de.asc; preference=encrypt --=-ba5r6Ds701NYq8n4AnLV Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2026-09-04 at 23:54 +0000, Markus Probst wrote: > If `Driver::probe` fails, the pointer to the driver data (`PrivateData`) > will first be set to NULL by `drvdata_obtain` and only after that the > serdev device will be closed by Drop. Thus there is a small window in > which the serdev device is still open, but the pointer to the driver data > is NULL. Therefore it is possible that `receive_buf_callback` might try t= o > access the `active` mutex on a null pointer. It seems, Sashiko found the same issue in a different unrelated place too (while reviewing this patch): https://sashiko.dev/#/patchset/20260905-rust_serdev_fix-v1-1-2ea92b154a6b%4= 0posteo.de Unfortunately, I cannot fix this one so easily, because the serdev device needs to be open for the entire lifetime of the "real" driver data (Driver::Data). Thanks - Markus Probst >=20 > Add a separate `ScopeGuard` that will close the device before the driver > data will be set to NULL on probe failure. >=20 > Fixes: 99f59aa82341 ("rust: add basic serial device bus abstractions") > Reported-by: Sashiko Bot > Closes: https://lore.kernel.org/linux-serial/20260903222159.70A911F000E9@= smtp.kernel.org/ > Signed-off-by: Markus Probst > --- > Unfortunately, this also makes the code in probe even more convoluted > than it already is. I will submit a patch (for the next merge cycle) > soon, which will address this concern. > --- > rust/kernel/serdev.rs | 20 ++++++++++++++++---- > 1 file changed, 16 insertions(+), 4 deletions(-) >=20 > diff --git a/rust/kernel/serdev.rs b/rust/kernel/serdev.rs > index 17ca504b7f8d..4f57f4c45329 100644 > --- a/rust/kernel/serdev.rs > +++ b/rust/kernel/serdev.rs > @@ -190,6 +190,16 @@ extern "C" fn probe_callback(sdev: *mut bindings::se= rdev_device) -> kernel::ffi: > // SAFETY: We have exclusive access to `private_data.open`. > unsafe { *private_data.open.get() =3D true }; > =20 > + let open_guard =3D ScopeGuard::new(|| { > + // SAFETY: > + // - `private_data.sdev.as_raw()` is guaranteed to be a = pointer to a valid > + // `struct serdev_device`. > + // - We just opened the device, thus it is guaranteed to= be open. > + unsafe { bindings::serdev_device_close(private_data.sdev= .as_raw()) }; > + // SAFETY: We have exclusive access to `private_data.ope= n`. > + unsafe { *private_data.open.get() =3D false }; > + }); > + > let data =3D T::probe(sdev, info); > =20 > // SAFETY: We have exclusive access to `private_data.driver`= . > @@ -203,10 +213,12 @@ extern "C" fn probe_callback(sdev: *mut bindings::s= erdev_device) -> kernel::ffi: > =20 > drop(active); > =20 > - result.map(|()| { > - private_data.dismiss(); > - 0 > - }) > + result?; > + > + open_guard.dismiss(); > + private_data.dismiss(); > + > + Ok(0) > }) > } > =20 >=20 > --- > base-commit: e5e04726cdd043e309677071ab1b65a4b18f422b > change-id: 20260904-rust_serdev_fix-be3ff9c8a5e8 --=-ba5r6Ds701NYq8n4AnLV Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iQJPBAABCAA5FiEEgnQYxPSsWOdyMMRzNHYf+OetQ9IFAmqbYLMbFIAAAAAABAAO bWFudTIsMi41KzEuMTIsMiwyAAoJEDR2H/jnrUPSfgEP/i6+AVvUF3DqH4KPzANY lQxCfnQ6YihdUcZqxdMK6q7060z/70SLiAeo74SDBOmywI8lpZf7SjZr6y7FHLl7 1FvGiHYtX2WoNzVJdDn0NfEq8z/MZlEvY22eRVnlF0EXLSBxcxpUVhl26A0EFsBz khMHRTRKaEj15m+Fuoxuy5TeEKLDE/H9zRvM1FfkGsTskuFUbCjdaelnX8O1ddHE Vg1p1dO7n93Rma7hM0a0IGVAJiaoNIO6aIofkMmrCsb3tH1JHwzMR0MhN1R6Nrhu lZ7KGy0NeVkIqynw907VxwB/8j3G2BuWnfP372OCTXWTQVdRL4+k+cc+dwcWoclm cTbeTCZIs+bX4LJ4lBuo1IV9+d/0ZroWGJHMMZwTD4iAWgTPCBy2tdr2IMah/3Uj YBg067irDbs04bvuEK006NAtZnZsSfc3ucblOndhTi9yMFL2cY4LkdVULOVQn/Qk DbDRz1LYf0rxTbnpVBuAvcQIGu97d7fUZMayxBfcpfGVDxWJdJWl3XU4qsqHRQfx XT58FmhwPIjYekUcAZ76spYDQPnjPLBvl3j2AnJTav4p6RY91rqNBOa7EPQiZEF2 EBtM20N9sH6NBMsiKKv+2+b/L4nZHt77qpiXbkZULqNBAI7cX38S7n6O8FT3uqri zetB5vh5bJfhDNmdV1gEo9pP =hU1N -----END PGP SIGNATURE----- --=-ba5r6Ds701NYq8n4AnLV--