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author | Chinmay Agarwal <chinagar@codeaurora.org> | 2021-01-27 22:24:54 +0530 |
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committer | Jakub Kicinski <kuba@kernel.org> | 2021-01-30 11:09:07 -0800 |
commit | eb4e8fac00d1e01ada5e57c05d24739156086677 (patch) | |
tree | 10e4c76da4170395687c74fde7203010df92dd95 /net/core | |
parent | 5399d52233c47905bbf97dcbaa2d7a9cc31670ba (diff) | |
download | linux-eb4e8fac00d1e01ada5e57c05d24739156086677.tar.bz2 |
neighbour: Prevent a dead entry from updating gc_list
Following race condition was detected:
<CPU A, t0> - neigh_flush_dev() is under execution and calls
neigh_mark_dead(n) marking the neighbour entry 'n' as dead.
<CPU B, t1> - Executing: __netif_receive_skb() ->
__netif_receive_skb_core() -> arp_rcv() -> arp_process().arp_process()
calls __neigh_lookup() which takes a reference on neighbour entry 'n'.
<CPU A, t2> - Moves further along neigh_flush_dev() and calls
neigh_cleanup_and_release(n), but since reference count increased in t2,
'n' couldn't be destroyed.
<CPU B, t3> - Moves further along, arp_process() and calls
neigh_update()-> __neigh_update() -> neigh_update_gc_list(), which adds
the neighbour entry back in gc_list(neigh_mark_dead(), removed it
earlier in t0 from gc_list)
<CPU B, t4> - arp_process() finally calls neigh_release(n), destroying
the neighbour entry.
This leads to 'n' still being part of gc_list, but the actual
neighbour structure has been freed.
The situation can be prevented from happening if we disallow a dead
entry to have any possibility of updating gc_list. This is what the
patch intends to achieve.
Fixes: 9c29a2f55ec0 ("neighbor: Fix locking order for gc_list changes")
Signed-off-by: Chinmay Agarwal <chinagar@codeaurora.org>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20210127165453.GA20514@chinagar-linux.qualcomm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/core')
-rw-r--r-- | net/core/neighbour.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 277ed854aef1..6d2d557442dc 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -1245,13 +1245,14 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr, old = neigh->nud_state; err = -EPERM; - if (!(flags & NEIGH_UPDATE_F_ADMIN) && - (old & (NUD_NOARP | NUD_PERMANENT))) - goto out; if (neigh->dead) { NL_SET_ERR_MSG(extack, "Neighbor entry is now dead"); + new = old; goto out; } + if (!(flags & NEIGH_UPDATE_F_ADMIN) && + (old & (NUD_NOARP | NUD_PERMANENT))) + goto out; ext_learn_change = neigh_update_ext_learned(neigh, flags, ¬ify); |