6.4-stable review patch. If anyone has any objections, please let me know.
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From: Liam R. Howlett Liam.Howlett@oracle.com
[ Upstream commit cfeb6ae8bcb96ccf674724f223661bbcef7b0d0b ]
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 Liam.Howlett@oracle.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- lib/maple_tree.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/lib/maple_tree.c b/lib/maple_tree.c index bb28a49d173c0..3315eaf93f563 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -4315,6 +4315,9 @@ 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->index != wr_mas->r_min) && (mas->last == wr_mas->r_max)) { if (new_end < node_pivots) wr_mas->pivots[new_end] = wr_mas->pivots[end];