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authorSven Eckelmann <sven@narfation.org>2019-02-23 14:27:10 +0100
committerSimon Wunderlich <sw@simonwunderlich.de>2019-03-25 09:31:19 +0100
commit3d65b9accab4a7ed5038f6df403fbd5e298398c7 (patch)
tree8e9e85033a81ef4ffa595e884fc9bb8e281ce72f /lib/dynamic_debug.c
parent4ba104f468bbfc27362c393815d03aa18fb7a20f (diff)
batman-adv: Reduce tt_local hash refcnt only for removed entry
The batadv_hash_remove is a function which searches the hashtable for an entry using a needle, a hashtable bucket selection function and a compare function. It will lock the bucket list and delete an entry when the compare function matches it with the needle. It returns the pointer to the hlist_node which matches or NULL when no entry matches the needle. The batadv_tt_local_remove is not itself protected in anyway to avoid that any other function is modifying the hashtable between the search for the entry and the call to batadv_hash_remove. It can therefore happen that the entry either doesn't exist anymore or an entry was deleted which is not the same object as the needle. In such an situation, the reference counter (for the reference stored in the hashtable) must not be reduced for the needle. Instead the reference counter of the actually removed entry has to be reduced. Otherwise the reference counter will underflow and the object might be freed before all its references were dropped. The kref helpers reported this problem as: refcount_t: underflow; use-after-free. Fixes: ef72706a0543 ("batman-adv: protect tt_local_entry from concurrent delete events") Signed-off-by: Sven Eckelmann <sven@narfation.org> Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Diffstat (limited to 'lib/dynamic_debug.c')
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