From: Al Viro Date: Wed, 8 Jun 2016 01:26:55 +0000 (-0400) Subject: fix d_walk()/non-delayed __d_free() race X-Git-Tag: v3.2.82~50 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=37f4f9e677576c8f8add9f43844c6c468caf8252 fix d_walk()/non-delayed __d_free() race commit 3d56c25e3bb0726a5c5e16fc2d9e38f8ed763085 upstream. Ascend-to-parent logics in d_walk() depends on all encountered child dentries not getting freed without an RCU delay. Unfortunately, in quite a few cases it is not true, with hard-to-hit oopsable race as the result. Fortunately, the fix is simiple; right now the rule is "if it ever been hashed, freeing must be delayed" and changing it to "if it ever had a parent, freeing must be delayed" closes that hole and covers all cases the old rule used to cover. Moreover, pipes and sockets remain _not_ covered, so we do not introduce RCU delay in the cases which are the reason for having that delay conditional in the first place. Signed-off-by: Al Viro [bwh: Backported to 3.2: - Adjust context - Also set the flag in __d_materialise_dentry())] Signed-off-by: Ben Hutchings --- Reading git-diff-tree failed