From d59070d1076ec5114edb67c87658aeb1d691d381 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Fri, 11 Aug 2023 15:10:13 +0200 Subject: radix tree: remove unused variable Recent versions of clang warn about an unused variable, though older versions saw the 'slot++' as a use and did not warn: radix-tree.c:1136:50: error: parameter 'slot' set but not used [-Werror,-Wunused-but-set-parameter] It's clearly not needed any more, so just remove it. Link: https://lkml.kernel.org/r/20230811131023.2226509-1-arnd@kernel.org Fixes: 3a08cd52c37c7 ("radix tree: Remove multiorder support") Signed-off-by: Arnd Bergmann Cc: Matthew Wilcox Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Peng Zhang Cc: Rong Tao Cc: Tom Rix Cc: Signed-off-by: Andrew Morton --- lib/radix-tree.c | 1 - 1 file changed, 1 deletion(-) (limited to 'lib') diff --git a/lib/radix-tree.c b/lib/radix-tree.c index 1a31065b2036..976b9bd02a1b 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -1136,7 +1136,6 @@ static void set_iter_tags(struct radix_tree_iter *iter, void __rcu **radix_tree_iter_resume(void __rcu **slot, struct radix_tree_iter *iter) { - slot++; iter->index = __radix_tree_iter_add(iter, 1); iter->next_index = iter->index; iter->tags = 0; -- cgit From cfeb6ae8bcb96ccf674724f223661bbcef7b0d0b Mon Sep 17 00:00:00 2001 From: "Liam R. Howlett" Date: Fri, 18 Aug 2023 20:43:55 -0400 Subject: maple_tree: disable mas_wr_append() when other readers are possible The current implementation of append may cause duplicate data and/or incorrect ranges to be returned to a reader during an update. Although this has not been reported or seen, disable the append write operation while the tree is in rcu mode out of an abundance of caution. During the analysis of the mas_next_slot() the following was artificially created by separating the writer and reader code: Writer: reader: mas_wr_append set end pivot updates end metata Detects write to last slot last slot write is to start of slot store current contents in slot overwrite old end pivot mas_next_slot(): read end metadata read old end pivot return with incorrect range store new value Alternatively: Writer: reader: mas_wr_append set end pivot updates end metata Detects write to last slot last lost write to end of slot store value mas_next_slot(): read end metadata read old end pivot read new end pivot return with incorrect range set old end pivot There may be other accesses that are not safe since we are now updating both metadata and pointers, so disabling append if there could be rcu readers is the safest action. Link: https://lkml.kernel.org/r/20230819004356.1454718-2-Liam.Howlett@oracle.com Fixes: 54a611b60590 ("Maple Tree: add new data structure") Signed-off-by: Liam R. Howlett Cc: Signed-off-by: Andrew Morton --- lib/maple_tree.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'lib') diff --git a/lib/maple_tree.c b/lib/maple_tree.c index 4dd73cf936a6..f723024e1426 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -4265,6 +4265,10 @@ static inline unsigned char mas_wr_new_end(struct ma_wr_state *wr_mas) * mas_wr_append: Attempt to append * @wr_mas: the maple write state * + * This is currently unsafe in rcu mode since the end of the node may be cached + * by readers while the node contents may be updated which could result in + * inaccurate information. + * * Return: True if appended, false otherwise */ static inline bool mas_wr_append(struct ma_wr_state *wr_mas) @@ -4274,6 +4278,9 @@ static inline bool mas_wr_append(struct ma_wr_state *wr_mas) struct ma_state *mas = wr_mas->mas; unsigned char node_pivots = mt_pivots[wr_mas->type]; + if (mt_in_rcu(mas->tree)) + return false; + if (mas->offset != wr_mas->node_end) return false; -- cgit