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Wed, 16 Sep 2026 13:22:02 +0000 (GMT) Received: from t83lp71.lnxne.boe (unknown [9.87.84.240]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 16 Sep 2026 13:22:02 +0000 (GMT) From: Nagamani PV To: andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: wintera@linux.ibm.com, aswin@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, kees@kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org, Nagamani PV , stable@vger.kernel.org, Sashiko Subject: [PATCH net v2 2/2] s390/ctcm: Fix use-after-free in channel_remove() Date: Wed, 16 Sep 2026 15:21:49 +0200 Message-ID: <20260916132149.4185912-3-nagamani@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260916132149.4185912-1-nagamani@linux.ibm.com> References: <20260907144511.3810194-1-nagamani@linux.ibm.com> <20260916132149.4185912-1-nagamani@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTE2MDE3NCBTYWx0ZWRfX5GfdOOnBZtzh NDGFi9u6wHWBkhPgIU8Jr6ey71HDV7dJ7/1uArG9+1bjIGwBhNglN484K2WQxx+EhG+h5wL9tHG Pk1UXgwMvZvSd9OG+jV1EWPFiNdmkbo3XDwDMtURVCL/gk1ISKQ7vQPNQmv/pMGWfmmTjrCI92d fegNhCjHPi+MGZcxJtD1YQwFp57fm8EWUAkQGKpmk719T+tBjfeRfkImO3s11xiBce9knpNSvDA V+7oJEQHihlyPyGBAvpxfoTbQLMsPS6y8OGF0Qt+aBcu6WY4/a0sUhHS1JWH/Ncc1IdafYJsk3u OMIxc9R8k5CwLTmvHiFi26fGDpNfdIt+07H6SQeOQZFl1VkGBSARZOSFPNFMCbg8pk1ofDEeI5F 96X0Z6xqVg95Llao+yfSc9YWJ9UMDK4DmykS8edr9zGAyqVHx9b1zZNcmprHlx/bkk55r5iN1EX ND1iMlhroQviXIOw7mw== X-Proofpoint-GUID: ts1csgUY5ESGtZPaXa5PB3U-Fk06qYN6 X-Authority-Analysis: v=2.4 cv=DobDa2/+ c=1 sm=1 tr=0 ts=6aaa97ff cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=c92rfblmAAAA:8 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=lm3vwLJbPXUmvxTiMesA:9 a=GvGzcOZaWPEFPQC_NcjD:22 X-Proofpoint-ORIG-GUID: BcD1n5l4LtNLdzjQbQuzzidkCX-Ot8wa X-Proofpoint-Spam-Info: AW1haW4tMjYwOTE2MDE3NCBTYWx0ZWRfX9kPa5Al+JpwG Nc7gZwxcfxNplSlEl3wjBEvA4Jfx+dW1nodNFtYeCQRMKN514Spo9izl6zmbiPIqgvDD4Pbn790 e1jWvXDouXyEA/YE8suwmR2n92qrW9M= 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=2026-09-16_02,2026-09-15_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 malwarescore=0 priorityscore=1501 suspectscore=0 impostorscore=0 spamscore=0 clxscore=1015 adultscore=0 bulkscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609160174 channel_remove() calls fsm_deltimer() which internally uses timer_delete(), then immediately frees the channel structure: fsm_deltimer(&ch->timer); kfree_fsm(ch->fsm); /* freed while callback may still run */ kfree(ch); timer_delete() returns immediately even if the timer callback is currently executing on another CPU, creating a window where fsm_expire_timer() accesses this->fi (which points to ch->fsm) after it has been freed by kfree_fsm(). Fix this by calling timer_delete_sync() directly on the underlying timer_list fields before freeing, instead of going through fsm_deltimer(). timer_delete_sync() is used rather than timer_shutdown_sync() because the channel is fully torn down by channel_remove() and the timer is never re-armed after this point, making the re-arm prevention of timer_shutdown_sync() unnecessary. This cannot be fixed in fsm_deltimer() itself because FSM action functions triggered by CTC_EVENT_TIMER call fsm_deltimer() from within the timer callback chain, which would cause a self-deadlock in timer_delete_sync(). Fixes: 293d984f0e36 ("ctcm: infrastructure for replaced ctc driver") Cc: stable@vger.kernel.org Reported-by: Sashiko Link: https://sashiko.dev/#/patchset/20260803182736.2356374-1-nagamani@linux.ibm.com?part=1 Reviewed-by: Aswin Karuvally Tested-by: Aswin Karuvally Signed-off-by: Nagamani PV --- Changes in v2: - add Fixes: and Cc: stable@vger.kernel.org tags (Sashiko netdev-bot) --- drivers/s390/net/ctcm_main.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/s390/net/ctcm_main.c b/drivers/s390/net/ctcm_main.c index 8b0d76a47d9f..63f8832f9b14 100644 --- a/drivers/s390/net/ctcm_main.c +++ b/drivers/s390/net/ctcm_main.c @@ -211,9 +211,9 @@ static void channel_remove(struct channel *ch) while (*c) { if (*c == ch) { *c = ch->next; - fsm_deltimer(&ch->timer); + timer_delete_sync(&ch->timer.tl); if (IS_MPC(ch)) - fsm_deltimer(&ch->sweep_timer); + timer_delete_sync(&ch->sweep_timer.tl); kfree_fsm(ch->fsm); clear_normalized_cda(&ch->ccw[4]); -- 2.53.0