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Howlett" Cc: Jann Horn , Alexei Starovoitov , 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, jolsa@kernel.org, akpm@linux-foundation.org, surenb@google.com, david@kernel.org, vbabka@kernel.org, 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-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 5121E80019 X-Stat-Signature: ruhzfc3um5zcbniuk39e8zmjasujq477 X-Spam-Status: No, score=-11.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1792764428-739848 X-HE-Meta: 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 oeoiXNBY nX16jYM2prFE5oRyXCvdpZZu1hVAY5javRvQ9bnlMmyTUc4nje9qWl8UF845P1mP40Q6icRbhc+TiP7ODlxVzxe28lDN6fv7la6a99//EfyvZSX9I0MEUS/oYZX2Ri+isYfvZGL7/LWIc3RcH8yMHxrdnCToHZHsKufxpTrYJzcIOQrUpNtcDVNhpcHo+VW7SvLbkt0U0iIEwLiGQC0gp/VqYxaV8FwB78VGbWt/1e9D5ZnTZCjHf+q2C+SCQko4fkxaa8WPiD5J62FUXxdsUMdh0AQ//O5DBng8xlCx0dYl6Pz0xBaNmj7mBFN3iZ9x8Gz5CDwSowOOWFEMVVuzcWeRK32wnODsxbyF+GQ0P8AR8SwRCCysWLG8zmg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Oct 22, 2026 at 03:33:16PM -0400, Liam R. Howlett wrote: > On 26/10/22 07:56PM, Jann Horn wrote: > > On Thu, Oct 22, 2026 at 3:57 AM Alexei Starovoitov > > wrote: > > > @@ -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)); > > > > Not an issue with your patch, just FYI regarding this preexisting > > WARN_ON_ONCE(): > > A failing small GFP_KERNEL allocation could theoretically cause > > do_munmap() to fail; the VMA tree has the ugly quirk that you can't > > reliably _remove_ elements without memory allocation. > > During munmap() we may need an allocation of one or two vma(s) > (splitting a vma or punching a hole) - and those may have anon vma > chains that need to be allocated, we may need to allocate for uffd > reasons, and we may need to allocate for the maple tree. > > That said, this path exclusively uses GFP_KERNEL which means we will > invoke the shrinker. If the shrinker comes back unsuccessful, we will > invoke OOM. This either succeed or it does not matter (we'll kill this > task). But you'd still get the WARN_ON() in the 'does not matter' case right? > > The other two possibilities is that the OOM is disabled during > hibernate/suspend calls, or error injection caused the failure. Fatal signals too? Might be some other cases too there. In general I'd say this WARN_ON() is probably not helpful. -- Cheers, Lorenzo