Re: [PATCH] net: frag, fix race conditions in LRU list maintenance

[Florian Westphal]

Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx> wrote:
> This patch fixes race between inet_frag_lru_move() and inet_frag_lru_add()
> which was introduced in commit 3ef0eb0db4bf92c6d2510fe5c4dc51852746f206
> ("net: frag, move LRU list maintenance outside of rwlock")
> 
> One cpu already added new fragment queue into hash but not into LRU.
> Other cpu found it in hash and tries to move it to the end of LRU.
> This leads to NULL pointer dereference inside of list_move_tail().
>
> Another possible race condition is between inet_frag_lru_move() and
> inet_frag_lru_del(): move can happens after deletion.

True, thanks for fixing this problem.

> This patch initializes LRU list head before adding fragment into hash and
> inet_frag_lru_move() doesn't touches it if it's empty.

Acked-by: Florian Westphal <fw@xxxxxxxxx>
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