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[37.188.177.177]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-475671d02f5sm7790027f8f.28.2026.06.30.04.59.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jun 2026 04:59:36 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 30 Jun 2026 13:59:29 +0200 To: David Windsor Cc: mhiramat@kernel.org, oleg@redhat.com, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, shuah@kernel.org, rick.p.edgecombe@intel.com, linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] x86/uprobes: Keep shadow stack in sync for emulated CALLs Message-ID: References: <8b5b1c7407b98f31664ad7b6a6faf20d2d4a6cad.1782777969.git.dwindsor@gmail.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8b5b1c7407b98f31664ad7b6a6faf20d2d4a6cad.1782777969.git.dwindsor@gmail.com> On Mon, Jun 29, 2026 at 08:13:33PM -0400, David Windsor wrote: > Uprobe CALL emulation updates the normal user stack, but not the CET user > shadow stack. The subsequent RET then sees a stale shadow stack entry and > raises #CP. > > Update the relative CALL emulation and XOL CALL fixup paths to keep the > shadow stack in sync. > > Fixes: 488af8ea7131 ("x86/shstk: Wire in shadow stack interface") > Signed-off-by: David Windsor hi, lgtm Tested-by: Jiri Olsa Acked-by: Jiri Olsa jirka > --- > > v2: > - propagate error from shshk_update_last_frame() rather than returning > -ERESTART in default_post_xol_op(). (Oleg) > > v1: https://lore.kernel.org/all/20260622183109.1137245-1-dwindsor@gmail.com/ > > arch/x86/kernel/uprobes.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c > index ebb1baf1eb1d..d74bb54543b6 100644 > --- a/arch/x86/kernel/uprobes.c > +++ b/arch/x86/kernel/uprobes.c > @@ -1246,9 +1246,15 @@ static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs > long correction = utask->vaddr - utask->xol_vaddr; > regs->ip += correction; > } else if (auprobe->defparam.fixups & UPROBE_FIX_CALL) { > + unsigned long retaddr = utask->vaddr + auprobe->defparam.ilen; > + int err; > + > regs->sp += sizeof_long(regs); /* Pop incorrect return address */ > - if (emulate_push_stack(regs, utask->vaddr + auprobe->defparam.ilen)) > + if (emulate_push_stack(regs, retaddr)) > return -ERESTART; > + err = shstk_update_last_frame(retaddr); > + if (err) > + return err; > } > /* popf; tell the caller to not touch TF */ > if (auprobe->defparam.fixups & UPROBE_FIX_SETF) > @@ -1338,6 +1344,10 @@ static bool branch_emulate_op(struct arch_uprobe *auprobe, struct pt_regs *regs) > */ > if (emulate_push_stack(regs, new_ip)) > return false; > + if (shstk_push(new_ip) == -EFAULT) { > + regs->sp += sizeof_long(regs); > + return false; > + } > } else if (!check_jmp_cond(auprobe, regs)) { > offs = 0; > } > -- > 2.53.0 >