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Thu, 07 Nov 2019 12:17:07 -0800 (PST) From: Lee Jones To: gregkh@google.com Subject: [PATCH 03/10] mac80211: mesh: fix RCU warning Date: Thu, 7 Nov 2019 20:16:55 +0000 Message-Id: <20191107201702.27023-3-lee.jones@linaro.org> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191107201702.27023-1-lee.jones@linaro.org> References: <20191107201702.27023-1-lee.jones@linaro.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191107_121709_707657_920460EA X-CRM114-Status: GOOD ( 12.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sasha Levin , Johannes Berg , linux-kernel@vger.kernel.org, Thomas Pedersen , Lee Jones , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Thomas Pedersen [ Upstream commit 551842446ed695641a00782cd118cbb064a416a1 ] ifmsh->csa is an RCU-protected pointer. The writer context in ieee80211_mesh_finish_csa() is already mutually exclusive with wdev->sdata.mtx, but the RCU checker did not know this. Use rcu_dereference_protected() to avoid a warning. fixes the following warning: [ 12.519089] ============================= [ 12.520042] WARNING: suspicious RCU usage [ 12.520652] 5.1.0-rc7-wt+ #16 Tainted: G W [ 12.521409] ----------------------------- [ 12.521972] net/mac80211/mesh.c:1223 suspicious rcu_dereference_check() usage! [ 12.522928] other info that might help us debug this: [ 12.523984] rcu_scheduler_active = 2, debug_locks = 1 [ 12.524855] 5 locks held by kworker/u8:2/152: [ 12.525438] #0: 00000000057be08c ((wq_completion)phy0){+.+.}, at: process_one_work+0x1a2/0x620 [ 12.526607] #1: 0000000059c6b07a ((work_completion)(&sdata->csa_finalize_work)){+.+.}, at: process_one_work+0x1a2/0x620 [ 12.528001] #2: 00000000f184ba7d (&wdev->mtx){+.+.}, at: ieee80211_csa_finalize_work+0x2f/0x90 [ 12.529116] #3: 00000000831a1f54 (&local->mtx){+.+.}, at: ieee80211_csa_finalize_work+0x47/0x90 [ 12.530233] #4: 00000000fd06f988 (&local->chanctx_mtx){+.+.}, at: ieee80211_csa_finalize_work+0x51/0x90 Signed-off-by: Thomas Pedersen Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin Signed-off-by: Lee Jones Change-Id: I19313f756382b0078683036d50c6645dd8ab2bee --- net/mac80211/mesh.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c index a70c970a743a..06189c952291 100644 --- a/net/mac80211/mesh.c +++ b/net/mac80211/mesh.c @@ -1062,7 +1062,8 @@ int ieee80211_mesh_finish_csa(struct ieee80211_sub_if_data *sdata) ifmsh->chsw_ttl = 0; /* Remove the CSA and MCSP elements from the beacon */ - tmp_csa_settings = rcu_dereference(ifmsh->csa); + tmp_csa_settings = rcu_dereference_protected(ifmsh->csa, + lockdep_is_held(&sdata->wdev.mtx)); RCU_INIT_POINTER(ifmsh->csa, NULL); if (tmp_csa_settings) kfree_rcu(tmp_csa_settings, rcu_head); @@ -1084,6 +1085,8 @@ int ieee80211_mesh_csa_beacon(struct ieee80211_sub_if_data *sdata, struct mesh_csa_settings *tmp_csa_settings; int ret = 0; + lockdep_assert_held(&sdata->wdev.mtx); + tmp_csa_settings = kmalloc(sizeof(*tmp_csa_settings), GFP_ATOMIC); if (!tmp_csa_settings) -- 2.24.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel