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Tue, 07 Jul 2026 09:41:19 -0700 (PDT) Received: from LAPTOP-83ECOPAB.localdomain ([167.220.149.19]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-387d15f0c35sm1448027a91.8.2026.07.07.09.41.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2026 09:41:19 -0700 (PDT) From: "Cen Zhang (Microsoft)" To: herbert@gondor.apana.org.au, tgraf@suug.ch, akpm@linux-foundation.org Cc: linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, AutonomousCodeSecurity@microsoft.com, tgopinath@linux.microsoft.com, kys@microsoft.com, blbllhy@gmail.com Subject: [PATCH v3] lib/rhashtable: clear stale iter->p on table restart Date: Tue, 7 Jul 2026 12:41:15 -0400 Message-ID: <20260707164115.4979-1-blbllhy@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit rhashtable_walk_start_check() has two restart paths when resuming a walk. When iter->walker.tbl is valid, it re-validates iter->p against the table and sets iter->p = NULL if the object is gone. When iter->walker.tbl is NULL (table was freed during resize), it resets slot and skip but forgets to clear iter->p. rhashtable_walk_next() then dereferences the stale iter->p, reading freed memory. This is a use-after-free. Any caller that does multi-fragment rhashtable walks across walk_stop/walk_start boundaries is affected. Concrete cases include netlink_diag (__netlink_diag_dump in net/netlink/diag.c) and TIPC (tipc_nl_sk_walk in net/tipc/socket.c). Crash stack (netlink_diag): BUG: KASAN: slab-use-after-free in rhashtable_walk_next+0x365/0x3c0 Read of size 8 at addr ffff88801a9d2438 (freed kmalloc-2k, offset 1080) Call Trace: rhashtable_walk_next+0x365/0x3c0 (lib/rhashtable.c:1016) __netlink_diag_dump+0x160/0x760 (net/netlink/diag.c:122) netlink_diag_dump+0xc2/0x240 netlink_dump+0x5bc/0x1270 netlink_recvmsg+0x7a3/0x980 sock_recvmsg+0x1bc/0x200 __sys_recvfrom+0x1d4/0x2c0 Fixes: 5d240a8936f6 ("rhashtable: improve rhashtable_walk stability when stop/start used.") Reported-by: AutonomousCodeSecurity@microsoft.com Closes: https://lore.kernel.org/linux-crypto/CAB8m9Wh559e+=n8z51gB8DrbEyCc2mc0MgGjrRR6_VXBmU=2AQ@mail.gmail.com Signed-off-by: Cen Zhang (Microsoft) --- v3: Solved patch format issue v2: Fix commit subject in Fixes tag Link: https://lore.kernel.org/linux-crypto/CAB8m9Wh559e+=n8z51gB8DrbEyCc2mc0MgGjrRR6_VXBmU=2AQ@mail.gmail.com lib/rhashtable.c | 1 + 1 file changed, 1 insertion(+) diff --git a/lib/rhashtable.c b/lib/rhashtable.c index 40cfb38ac..d459bef24 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -878,6 +878,7 @@ int rhashtable_walk_start_check(struct rhashtable_iter *iter) iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht); iter->slot = 0; iter->skip = 0; + iter->p = NULL; return -EAGAIN; } -- 2.53.0