lock_parent: don't step on stale ->d_parent of all-but-freed one

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commit c2338f2dc7 upstream.

Dentry that had been through (or into) __dentry_kill() might be seen
by shrink_dentry_list(); that's normal, it'll be taken off the shrink
list and freed if __dentry_kill() has already finished.  The problem
is, its ->d_parent might be pointing to already freed dentry, so
lock_parent() needs to be careful.

We need to check that dentry hasn't already gone into __dentry_kill()
*and* grab rcu_read_lock() before dropping ->d_lock - the latter makes
sure that whatever we see in ->d_parent after dropping ->d_lock it
won't be freed until we drop rcu_read_lock().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Al Viro 2014-06-12 00:29:13 -04:00 • committed by Greg Kroah-Hartman

parent d3c8656bc2

commit 4e358517b2

1 changed files with 3 additions and 1 deletions

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fs/dcache.c

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