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Sat, 29 Aug 2026 06:01:33 +0000 (GMT) Received: from [9.67.115.193] (unknown [9.67.115.193]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Sat, 29 Aug 2026 06:01:32 +0000 (GMT) Message-ID: <987fa1d6-7328-467b-af7e-5c1c4ef1598d@linux.ibm.com> Date: Sat, 29 Aug 2026 11:31:30 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] powerpc/entry: Clear TIF_SYSCALL_RET before syscall error return To: Shrikanth Hegde , tglx@kernel.org, maddy@linux.ibm.com, linuxppc-dev@lists.ozlabs.org Cc: linux-kernel@vger.kernel.org, chleroy@kernel.org, mkchauras@gmail.com References: <20260828053811.1042300-1-sshegde@linux.ibm.com> Content-Language: en-US From: Shivaprasad G Bhat In-Reply-To: <20260828053811.1042300-1-sshegde@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=PPc/P/qC c=1 sm=1 tr=0 ts=6a9275c6 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=jdSCQhKvPWLdp4stf3gA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: HVjFEIdgwemuqmI9z8eU4-eJlZdy-LXo X-Proofpoint-ORIG-GUID: hcwM8te7jPxMa8-YShyZoik4gWAFLguC X-Proofpoint-Spam-Info: AW1haW4tMjYwODI5MDA1MCBTYWx0ZWRfX20sYYoqH7zAa KCAZeYYLTGkyVQ92/ogsDW+oYS3jgN0QxEVrvxJkEBKOAhIAZart7AqToJbIhwxTWoOsomgh7Im AV5gmyWugOC+NrLwFsSV6R/egx7zE4k= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODI5MDA1MCBTYWx0ZWRfX8ANJJ74W3K7h DrM/dTDpmqd5esQf7kdzXgDfdM1yy6v6cdMEYRb93pYvbqGfs/lhoIHjQcHapLI8yDmUUbDjGRb 2KighS+gIOTI6OK4PbU89aF8nzBYYyVguSNHVjkY7KgRJ/wxg3U9+lU7rui+PQY2tNUvsdvlhLO Xun+0WnnqFnYDcHJMjAfQH2DIV7s9ygRp2prZ2k6Jh2YV+fbxL9L501MTgaMXk3qThz+BEtt0Xb 75wGZA3/Uywb5l5U0iAvo38pkBvUNx9BgJBiNPpjE6zIqTdiCruypgkkm9aVSW3TctLKLvOwmey q0h5UEQmpMyrnbtUey19H5LBdP1XC4qUsBkgZL2kEWd14i74IW8OEZ5Kips1UvJo/R75cPTnGRz MVYaR5O0c45gLxJubyCuniG/emoz+Pgr0sSLGTyWeodrVwfMlSVDcKz7smMM/nZIqhFRJl4zo7r N4T5B6iqICaWuBPh7bw== 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=2026-08-29_02,2026-08-27_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 phishscore=0 adultscore=0 suspectscore=0 bulkscore=0 spamscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608290050 On 8/28/26 11:08 AM, Shrikanth Hegde wrote: > Shivaprasad reported a boot failure due to userspace processes crash on > abort() from libc.so.6. It was bisected to merge request > commit '3424d8c18a7d ("Merge tag 'core-entry-2026-08-17' of > git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip")' > > Upon checking the merge, when syscall_enter_from_user_mode_randomize_stack > fails, which could happen when a tracer like seccomp or ptrace intercepts > and skips the syscall, the code returns to userspace immediately without > clearing the intermediate flag which was set. > > When the next syscall is made, it immediately aborts the valid syscall > since the flag is still set. Hence clear the flag on occurrence of first > failure. > > Reported-by: Shivaprasad G Bhat > Closes: https://lore.kernel.org/all/e301014d-568f-4ed5-bc64-b8a85ca0b1e1@linux.ibm.com/ > Fixes: 3424d8c18a7d ("Merge tag 'core-entry-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip") > Signed-off-by: Shrikanth Hegde Tested-by: Shivaprasad G Bhat Thanks, Shivaprasad > --- > PS: I have kept the block below since earlier code was checking it > regardless of result of syscall_enter_from_user_mode. If it turns out > to be a redundant, it can be removed later. > > arch/powerpc/kernel/syscall.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c > index 4916c205c4bb..fbefe1927b10 100644 > --- a/arch/powerpc/kernel/syscall.c > +++ b/arch/powerpc/kernel/syscall.c > @@ -18,8 +18,10 @@ notrace long system_call_exception(struct pt_regs *regs, unsigned long r0) > long ret; > syscall_fn f; > > - if (unlikely(!syscall_enter_from_user_mode_randomize_stack(regs, &r0))) > + if (unlikely(!syscall_enter_from_user_mode_randomize_stack(regs, &r0))) { > + clear_thread_flag(TIF_SYSCALL_RET); > return syscall_get_error(current, regs); > + } > > if (unlikely(test_and_clear_thread_flag(TIF_SYSCALL_RET))) > return syscall_get_error(current, regs);