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Tue, 08 Sep 2026 06:14:00 -0700 (PDT) Received: from [127.0.0.1] ([2a09:bac6:37a9:1e5a::306:1]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c260d6e1c93sm625170866b.63.2026.09.08.06.13.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Sep 2026 06:14:00 -0700 (PDT) From: Caleb Kan Date: Tue, 08 Sep 2026 14:13:41 +0100 Subject: [PATCH RFC v2 08/11] scripts/gdb: reject trie-backed stack depot handles MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260908-stackdepot-trie-v2-8-1996d5cef732@cloudflare.com> References: <20260908-stackdepot-trie-v2-0-1996d5cef732@cloudflare.com> In-Reply-To: <20260908-stackdepot-trie-v2-0-1996d5cef732@cloudflare.com> To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Vlastimil Babka , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Andrey Konovalov , Oscar Salvador , Caleb Kan , kernel-team@cloudflare.com X-Mailer: b4 0.16.0 X-Rspam-User: X-Stat-Signature: ja5uqcsb3pqx19aa6yz3xhqsde5k7h7o X-Rspamd-Queue-Id: D37BA14000A X-Rspamd-Server: rspam07 X-HE-Tag: 1788873241-769846 X-HE-Meta: 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 UspDECG/ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Caleb Kan The lx-stack_depot_lookup command can reconstruct stacks only from contiguous hash-backed records. A later patch will encode trie-backed handles as dense stack IDs in pool_index_plus_1 and offset. Without an explicit check, a trie handle enters the hash-only out-of-bounds path. Reject pool_index_plus_1 values above stack_max_pools before looking up a hash pool, and report that trie-backed handles are unsupported. Supporting them would require the helper to walk the side table and parent links, which is left for future work. Signed-off-by: Caleb Kan --- scripts/gdb/linux/stackdepot.py | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/scripts/gdb/linux/stackdepot.py b/scripts/gdb/linux/stackdepot.py index 37313a5a51a0..82aeb9f532c3 100644 --- a/scripts/gdb/linux/stackdepot.py +++ b/scripts/gdb/linux/stackdepot.py @@ -37,6 +37,10 @@ def stack_depot_fetch(handle): if handle == 0: raise gdb.GdbError("handle is 0\n") + stack_max_pools = gdb.parse_and_eval('stack_max_pools') + if parts['pool_index_plus_1'] > stack_max_pools: + raise gdb.GdbError("trie-backed stack depot handles are not supported\n") + pool_index = parts['pool_index_plus_1'] - 1 if pool_index >= pools_num: gdb.write("pool index %d out of bounds (%d) for stack id 0x%08x\n" % (parts['pool_index'], pools_num, handle)) -- Git-155)