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[24.6.192.50]) by smtp.gmail.com with ESMTPSA id b202sm29493069pfb.88.2018.12.18.11.40.24 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 18 Dec 2018 11:40:25 -0800 (PST) From: frowand.list@gmail.com To: robh+dt@kernel.org, Michael Bringmann , linuxppc-dev@lists.ozlabs.org Cc: Michael Ellerman , Tyrel Datwyler , Thomas Falcon , Juliet Kim , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 2/2] of: __of_detach_node() - remove node from phandle cache Date: Tue, 18 Dec 2018 11:40:03 -0800 Message-Id: <1545162003-11577-3-git-send-email-frowand.list@gmail.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1545162003-11577-1-git-send-email-frowand.list@gmail.com> References: <1545162003-11577-1-git-send-email-frowand.list@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Frank Rowand Non-overlay dynamic devicetree node removal may leave the node in the phandle cache. Subsequent calls to of_find_node_by_phandle() will incorrectly find the stale entry. Remove the node from the cache. Add paranoia checks in of_find_node_by_phandle() as a second level of defense (do not return cached node if detached, do not add node to cache if detached). Fixes: 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of of_find_node_by_phandle()") Reported-by: Michael Bringmann Signed-off-by: Frank Rowand --- do not "cc: stable", unless the following commits are also in stable: commit e54192b48da7 ("of: fix phandle cache creation for DTs with no phandles") commit b9952b5218ad ("of: overlay: update phandle cache on overlay apply and remove") commit 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of of_find_node_by_phandle()") Changes since v2: - add temporary variable np in __of_free_phandle_cache_entry() to improve readability - explain reason for WARN_ON() in comment - add Fixes tag in patch comment drivers/of/base.c | 31 ++++++++++++++++++++++++++++++- drivers/of/dynamic.c | 3 +++ drivers/of/of_private.h | 4 ++++ 3 files changed, 37 insertions(+), 1 deletion(-) diff --git a/drivers/of/base.c b/drivers/of/base.c index 6c33d63361b8..6d20b6dcf034 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c @@ -162,6 +162,28 @@ int of_free_phandle_cache(void) late_initcall_sync(of_free_phandle_cache); #endif +/* + * Caller must hold devtree_lock. + */ +void __of_free_phandle_cache_entry(phandle handle) +{ + phandle masked_handle; + struct device_node *np; + + if (!handle) + return; + + masked_handle = handle & phandle_cache_mask; + + if (phandle_cache) { + np = phandle_cache[masked_handle]; + if (np && handle == np->phandle) { + of_node_put(np); + phandle_cache[masked_handle] = NULL; + } + } +} + void of_populate_phandle_cache(void) { unsigned long flags; @@ -1209,11 +1231,18 @@ struct device_node *of_find_node_by_phandle(phandle handle) if (phandle_cache[masked_handle] && handle == phandle_cache[masked_handle]->phandle) np = phandle_cache[masked_handle]; + if (np && of_node_check_flag(np, OF_DETACHED)) { + WARN_ON(1); /* did not uncache np on node removal */ + of_node_put(np); + phandle_cache[masked_handle] = NULL; + np = NULL; + } } if (!np) { for_each_of_allnodes(np) - if (np->phandle == handle) { + if (np->phandle == handle && + !of_node_check_flag(np, OF_DETACHED)) { if (phandle_cache) { /* will put when removed from cache */ of_node_get(np); diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c index f4f8ed9b5454..ecea92f68c87 100644 --- a/drivers/of/dynamic.c +++ b/drivers/of/dynamic.c @@ -268,6 +268,9 @@ void __of_detach_node(struct device_node *np) } of_node_set_flag(np, OF_DETACHED); + + /* race with of_find_node_by_phandle() prevented by devtree_lock */ + __of_free_phandle_cache_entry(np->phandle); } /** diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h index 5d1567025358..24786818e32e 100644 --- a/drivers/of/of_private.h +++ b/drivers/of/of_private.h @@ -84,6 +84,10 @@ static inline void __of_detach_node_sysfs(struct device_node *np) {} int of_resolve_phandles(struct device_node *tree); #endif +#if defined(CONFIG_OF_DYNAMIC) +void __of_free_phandle_cache_entry(phandle handle); +#endif + #if defined(CONFIG_OF_OVERLAY) void of_overlay_mutex_lock(void); void of_overlay_mutex_unlock(void); -- Frank Rowand