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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a97c42b3c1sm10693945e9.6.2026.10.27.19.15.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Oct 2026 19:15:18 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: sashiko-reviews@lists.linux.dev Cc: bpf@vger.kernel.org Subject: Re: [RFC PATCH bpf-next v1 09/11] bpf: Let the comparator of bpf_rbtree_add unwind Date: Wed, 28 Oct 2026 03:15:17 +0100 Message-ID: <20261028021517.1203900-7-memxor@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: 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=UTF-8 Content-Transfer-Encoding: 8bit On Wed Oct 28, 2026 at 2:21 AM CET, sashiko-bot wrote: > [...] > [Severity: High] > Does the unwound path in __bpf_rbtree_add() leave node->owner poisoned with > BPF_PTR_POISON when the object survives __bpf_obj_drop_impl()? Right: with another reference holding the node, the drop left it with its owner poisoned, and no add would take it again. The next version unlinks it first, as bpf_rb_root_free() does. > [...] > [Severity: Critical] > Can an unwinding comparator callback with a two-register return type clobber > caller->regs[BPF_REG_2] in prepare_func_exit(), causing check_kfunc_call() to > release the wrong reference ID and leave a dangling owning pointer to the > dropped node? Same as on 03/11: a callback hands over r0 alone in the next version, so r2 stays the node the revisit releases. > [...]