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Wed, 21 Oct 2026 18:57:41 -0700 (PDT) Received: from coder-ast-ast-dev-ml-0.tail2dda0.ts.net ([153.61.198.250]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ea3b4af4dasm17474295ad.75.2026.10.21.18.57.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Oct 2026 18:57:41 -0700 (PDT) From: Alexei Starovoitov To: bpf@vger.kernel.org Cc: daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, oleg@redhat.com, peterz@infradead.org, mhiramat@kernel.org, jolsa@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: [PATCH bpf-next 4/9] uprobes/x86: Don't WARN if an optimized probe can't be written Date: Thu, 22 Oct 2026 01:57:07 +0000 Message-ID: <20261022015712.1297331-5-alexei.starovoitov@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261022015712.1297331-1-alexei.starovoitov@gmail.com> References: <20261022015712.1297331-1-alexei.starovoitov@gmail.com> X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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