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powerpc/entry: Clear TIF_SYSCALL_RET before syscall error return

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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 <sbhat@linux.ibm.com>
Closes: https://lore.kernel.org/all/e301014d-568f-4ed5-bc64-b8a85ca0b1e1@linux.ibm.com/
Fixes: 3424d8c18a ("Merge tag 'core-entry-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip")
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Tested-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
Reviewed-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260828053811.1042300-1-sshegde@linux.ibm.com
This commit is contained in:
Shrikanth Hegde 2026-08-28 11:08:11 +05:30 committed by Madhavan Srinivasan
parent cee9395acd
commit 2c1dde8a69
1 changed files with 3 additions and 1 deletions
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4
arch/powerpc/kernel/syscall.c
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@ -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);