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Thu, 22 Oct 2026 07:56:48 +0000 (GMT) Received: from osiris (unknown [9.224.90.220]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTPS; Thu, 22 Oct 2026 07:56:48 +0000 (GMT) Date: Thu, 22 Oct 2026 09:56:46 +0200 From: Heiko Carstens To: sashiko-reviews@lists.linux.dev Cc: linux-s390@vger.kernel.org, Vasily Gorbik , Alexander Gordeev , Christian Borntraeger Subject: Re: [RFC PATCH] s390/syscall: Sign extend system call number retrieved via syscall_get_nr() Message-ID: <20261022075646.11120A92-hca@linux.ibm.com> References: <20261021125911.1550331-1-hca@linux.ibm.com> X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-GUID: Y-roT4I9BUAtqE8rQaD99HkLX_z5xa7b X-Proofpoint-Spam-Info: AW1haW4tMjYxMDIyMDAzMCBTYWx0ZWRfX2NkfHgfm4jiV q86brYIQ3/c5BTjOb4nB+Md7lCrQAjriFsbakKLwtYlLwbUzq2W4QKjsVufMtB34tFpI3zV07Vo k+p2ihZMzErUxI/OSOylzNYtdaKG/I8= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDIyMDAzMCBTYWx0ZWRfX6KukPcWu7bz2 aMxSVEnk/KlqFlBOE2KGzYZgjbpcvkxTOP2UswP8ella4ryvFWHsmb0D3EjspA9c+rnPfDYb0/0 YAJ76V74kXYkT1felEakFVWf6CY/3EJE/s6jBm8LMeVmisf2MFsJFT8cND8LNFnowtCiCbE318T 8EXj4o0xOhjBX6X/BwiISerkJJGGJssh//TrToBn2Q0pob6RE1box00IwDnn/VO+U3CUAQl0Sr2 phLlWEwSIPmuH3Ho6yvqnITWtGEmbkw3i4rZaEoQBrHbMPdOP1dSmC031eu2wlr6QLaXhAozMYa T84YfpH93Q5wDaBtzN23SZ+qO9t5reTX2vctQpghOefnpwQRt5r7MSK/shYR1YOgoHqUKKem6jt 5Gv4lGLnON4jZuLoW+avuMmdwBeO3e/IBgBFaphgwQzdJ24Qfo5qXB3RLLNZdZiFc9ercV6uodp +MLEKtyA28Ob8ejZi7w== X-Proofpoint-ORIG-GUID: Y-roT4I9BUAtqE8rQaD99HkLX_z5xa7b X-Authority-Analysis: v=2.4 cv=Ob4NnRTY c=1 sm=1 tr=0 ts=6ad9c1c6 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=kj9zAlcOel0A:10 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=AGpjq-OJZXGNhh8UPtcA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-10-22_03,2026-10-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 adultscore=0 phishscore=0 spamscore=0 suspectscore=0 lowpriorityscore=0 clxscore=1015 impostorscore=0 priorityscore=1501 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610190000 definitions=main-2610220030 On Wed, Oct 21, 2026 at 01:27:30PM +0000, sashiko-bot@kernel.org wrote: > > @@ -20,7 +20,7 @@ static inline long syscall_get_nr(struct task_struct *task, > > struct pt_regs *regs) > > { > > return test_pt_regs_flag(regs, PIF_SYSCALL) ? > > - (regs->int_code & 0xffff) : -1; > > + (s16)(regs->int_code & 0xffff) : -1; > > } > > [Severity: High] > When a system call is skipped under SECCOMP_RET_TRACE on s390, can this cause > __do_syscall() to return the wrong value to userspace instead of -ENOSYS? > > Previously, syscall_get_nr() returned an unsigned 16-bit value (65535 when nr > was set to -1), so after PTRACE_EVENT_SECCOMP in > kernel/seccomp.c:__seccomp_filter(): > > /* Check if the tracer forced the syscall to be skipped. */ > this_syscall = syscall_get_nr(current, current_pt_regs()); > if (this_syscall < 0) > goto skip; This is addressed with: https://lore.kernel.org/all/20261021085643.2442949-1-hca@linux.ibm.com/ Read: should not happen anymore. > [Severity: Medium] > Should arch/s390/kernel/syscall.c:__do_syscall() and > arch/s390/include/asm/syscall.h:syscall_set_nr() also be updated to keep the > syscall number representation consistent with syscall_get_nr()? > > In arch/s390/kernel/syscall.c:__do_syscall(): > > nr = regs->int_code & 0xffff; > if (likely(!nr)) { > nr = regs->gprs[1] & 0xffff; > regs->int_code &= ~0xffffUL; > regs->int_code |= nr; > } > regs->gprs[2] = nr; This is valid - things should be consistent.