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Fri, 23 Oct 2026 00:13:24 -0700 (PDT) Received: from krava ([2a02:8308:a00c:e200::25dc]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48e38025d76sm3155877f8f.13.2026.10.23.00.13.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Oct 2026 00:13:23 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Fri, 23 Oct 2026 09:13:21 +0200 To: Alexei Starovoitov Cc: bpf@vger.kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, oleg@redhat.com, peterz@infradead.org, mhiramat@kernel.org, akpm@linux-foundation.org, liam@infradead.org, ljs@kernel.org, surenb@google.com, david@kernel.org, vbabka@kernel.org, jannh@google.com, hughd@google.com, kees@kernel.org, mingo@redhat.com, tglx@kernel.org, x86@kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next 4/9] uprobes/x86: Don't WARN if an optimized probe can't be written Message-ID: References: <20261022015712.1297331-1-alexei.starovoitov@gmail.com> <20261022015712.1297331-5-alexei.starovoitov@gmail.com> X-Mailing-List: bpf@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: <20261022015712.1297331-5-alexei.starovoitov@gmail.com> On Thu, Oct 22, 2026 at 01:57:07AM +0000, Alexei Starovoitov wrote: > From: Alexei Starovoitov > > __arch_uprobe_optimize() and set_orig_insn() do WARN_ON_ONCE() when > uprobe_write() fails, and user space can make it fail: > - -EINTR from get_user_pages_remote() when current is being killed. > - -ENOMEM when COW can't be broken, since memcg is at its limit. > - -EINVAL from __update_ref_ctr() when the process cleared the semaphore > of SDT probe. > > Kill the processes that call probed nop10. It warns in 8 of 8 runs: > > WARNING: arch/x86/kernel/uprobes.c:1186 at arch_uprobe_optimize+0x291/0x3a0 > uprobe_notify_resume+0x1c3/0x4c0 > exit_to_user_mode_loop+0x63/0x4e0 > exc_int3+0x1f3/0x250 > > The next patch calls set_orig_insn() from fork(). Kill the processes that > fork and keep mmap_lock busy, while a trace event on nop10 is enabled and > disabled. The kernel with the next two patches and without this one warns > in 3 of 3 runs. The whole series in 0 of 3: > > WARNING: arch/x86/kernel/uprobes.c:1161 at set_orig_insn+0x161/0x170 > register_one_mm+0x154/0x180 > uprobe_dup_mmap+0x61/0xb0 > dup_mmap+0x149/0x9f0 > > The callers handle the error. arch_uprobe_optimize() marks uprobe as not > optimizable and byte 0 stays a breakpoint. set_orig_insn() returns > the error. Drop both WARNs. > > This depends on the previous patch. Without it WARN was the only sign of > the bytes that set_orig_insn() cannot restore. Hence no Fixes tag. > > Signed-off-by: Alexei Starovoitov Acked-by: Jiri Olsa thanks, jirka > --- > arch/x86/kernel/uprobes.c | 9 +++------ > 1 file changed, 3 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c > index 62bbe41c6466..33c35bf07801 100644 > --- a/arch/x86/kernel/uprobes.c > +++ b/arch/x86/kernel/uprobes.c > @@ -1170,11 +1170,8 @@ int set_orig_insn(struct arch_uprobe *auprobe, struct vm_area_struct *vma, > int ret = is_optimized(vma->vm_mm, vaddr); > if (ret < 0) > return ret; > - if (ret) { > - ret = swbp_unoptimize(auprobe, vma, vaddr); > - WARN_ON_ONCE(ret); > - return ret; > - } > + if (ret) > + return swbp_unoptimize(auprobe, vma, vaddr); > } > return uprobe_write_opcode(auprobe, vma, vaddr, *(uprobe_opcode_t *)&auprobe->insn, > false /* is_register */); > @@ -1197,7 +1194,7 @@ static int __arch_uprobe_optimize(struct arch_uprobe *auprobe, struct mm_struct > if (IS_ERR(tramp)) > return PTR_ERR(tramp); > ret = swbp_optimize(auprobe, vma, vaddr, tramp->vm_start); > - if (WARN_ON_ONCE(ret) && new_mapping) > + if (ret && new_mapping) > WARN_ON_ONCE(do_munmap(mm, tramp->vm_start, PAGE_SIZE, NULL)); > return ret; > } > -- > 2.55.0 >