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Fri, 21 Aug 2026 09:01:44 +0000 (GMT) Received: from ltc.linux.ibm.com (unknown [9.5.196.140]) by smtpav06.dal12v.mail.ibm.com (Postfix) with ESMTP; Fri, 21 Aug 2026 09:01:43 +0000 (GMT) Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Fri, 21 Aug 2026 11:01:43 +0200 From: Harald Freudenberger To: sashiko-reviews@lists.linux.dev Cc: Heiko Carstens , Alexander Gordeev , Christian Borntraeger , linux-s390@vger.kernel.org, Vasily Gorbik Subject: Re: [PATCH v6 3/9] s390/crypto: Fix use of mutex in atomic context in PAES Reply-To: freude@linux.ibm.com Mail-Reply-To: freude@linux.ibm.com In-Reply-To: <20260821085635.D6BC61F000E9@smtp.kernel.org> References: <20260821084648.23222-1-freude@linux.ibm.com> <20260821084648.23222-4-freude@linux.ibm.com> <20260821085635.D6BC61F000E9@smtp.kernel.org> Message-ID: <5f077680b9797530ea64aef75ff56f8f@linux.ibm.com> X-Sender: freude@linux.ibm.com Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=CpuPtH4D c=1 sm=1 tr=0 ts=6a8813fb cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=kj9zAlcOel0A:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=6YwGb265LKlJqqV16GsA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: qBiX0V6rdCf54tm9RMEvq2SUD8LzzSoo X-Proofpoint-GUID: qBiX0V6rdCf54tm9RMEvq2SUD8LzzSoo X-Proofpoint-Spam-Info: AW1haW4tMjYwODIxMDA2NiBTYWx0ZWRfXyMKrx+RTYTQm aqe/5Xnom9Gn7r2nGtsZeulz4DCQSc7UT9e1kVBeN+NqCkYZK56E2i2r7+ou6pqCS5nhMfbOOp2 ZOCLDgTS2G+yNZoihU2VMhcuOWOLDnA= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODIxMDA2NiBTYWx0ZWRfXz4e1rl/gxUUW FSJKpSXFhQREG3ezY+Pl+jYLH8KI5oz39xyRoxtdhwAcFm/328mdcaJajP9hrLy+cbMORQ7mRqn dBdF/BI6YohsBmglt2krgfHKYo06nzjg2NXJR5xP7No0a9WM/G5wFjbwfYC0w/7ynCfCneownvU CNTm9h7tOEXNcpawfL8ZeMFVA9SWdPC6Wv2ZjmjxI8OSIOQpcWXFjQRCnFo1XU5NNkOwlndHGya kmGm1Y3TGB1Cp7+zSaDbi8x/r2O55lStyLKDO4RwBtgQXpuD8f8QDASoa+4KC+FGAMeppBBq66N IADMRuQ1LhWcxAm5qKlvjv1PQfXnyvmXXLA/uIXo6gqXdIbUMHy+K6b1fDGtuTE8KCeawpEXAAc VbL5DkaRPbjW3bfif9l09aduYl4TbUIOEmVnrAPKqcnEWYlSpi0+DriTpfoyu8z1nWcPD/NlHYa sg74LKpX1uRD6kvm0iQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-21_02,2026-08-21_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 adultscore=0 bulkscore=0 malwarescore=0 phishscore=0 lowpriorityscore=0 spamscore=0 clxscore=1015 priorityscore=1501 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608210066 On 2026-08-21 10:56, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential > issue(s) to consider: > > Pre-existing issues: > - [High] The `aes_s390.c` module contains the exact same locking bug > in atomic context that this patch fixes in `paes_s390.c`. The > `ctr_aes_crypt()` function uses `mutex_trylock(&ctrblk_lock)` and > subsequently calls `mutex_unlock(&ctrblk_lock)`. As the patch's commit > message notes, mutexes are not safe to use in atomic or interrupt > context. Synchronous skcipher algorithms like `ctr-aes-s390` can be > invoked directly from `softirq` context (e.g., by the IPsec stack). > Calling `mutex_unlock()` in `softirq` is a strict violation of kernel > locking rules. > -- > > --- Patch [3]: [PATCH v6 3/9] s390/crypto: Fix use of mutex in atomic > context in PAES --- > commit 425e8f1d3532a176433992d286f917e0fd14ff9e > Author: Harald Freudenberger > > s390/crypto: Fix use of mutex in atomic context in PAES > > This commit fixes a locking issue in the PAES CTR implementation where > a > mutex was used in atomic or interrupt context. It replaces the mutex > with > a binary semaphore which is safe to use in such environments. > >> diff --git a/arch/s390/crypto/paes_s390.c >> b/arch/s390/crypto/paes_s390.c >> --- a/arch/s390/crypto/paes_s390.c >> +++ b/arch/s390/crypto/paes_s390.c > [ ... ] >> @@ -45,7 +45,7 @@ module_param_named(clrkey, pkey_clrkey_allowed, >> bool, 0444); >> MODULE_PARM_DESC(clrkey, "Allow clear key material (default N)"); >> >> static u8 *ctrblk; >> -static DEFINE_MUTEX(ctrblk_lock); >> +static DEFINE_SEMAPHORE(ctrblk_sem, 1); > > [Severity: High] > This isn't a bug introduced by this patch, but > arch/s390/crypto/aes_s390.c > appears to have the exact same bug that this patch is fixing here. > > Looking at ctr_aes_crypt() in aes_s390.c: > > locked = mutex_trylock(&ctrblk_lock); > > ret = skcipher_walk_virt(&walk, req, false); > while ((nbytes = walk.nbytes) >= AES_BLOCK_SIZE) { > ... > } > if (locked) > mutex_unlock(&ctrblk_lock); > > Since synchronous skcipher algorithms like ctr-aes-s390 can be invoked > from > softirq context (such as by the IPsec stack), would calling > mutex_unlock() > here trigger a lockdep splat or crash, especially on PREEMPT_RT where > mutex_unlock() must be called from process context? > > Does aes_s390.c also need to be converted to use a binary semaphore? Allready addressed and fixed with the aes_s390 patch series.