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libfc: sanity check cpu number extracted from xid

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In the receive path libfc extracts a cpu number from the ox_id in the
fiber channel header and uses that to do a per_cpu_ptr conversion.  If,
for some reason, a frame is received with an invalid ox_id, per_cpu_ptr
will return an invalid pointer and the libfc receive path will panic the
system trying to use it.

I'm currently looking at such a case, and I don't yet know why a cpu
number > nr_cpu_ids is appearing in an exchange id.  But adding a sanity
check in libfc prevents a system panic, and seems like good idea when
dealing with frames coming in from the network.

Signed-off-by: Chris Leech <cleech@redhat.com>
Acked-by: Johannes Thumshirn <jth@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Chris Leech 2016-06-30 08:32:36 -07:00 committed by Martin K. Petersen
parent 4b9bc86d5a
commit fa06883281
1 changed files with 9 additions and 1 deletions
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10
drivers/scsi/libfc/fc_exch.c
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@ -908,9 +908,17 @@ static struct fc_exch *fc_exch_find(struct fc_exch_mgr *mp, u16 xid)
{
struct fc_exch_pool *pool;
struct fc_exch *ep = NULL;
u16 cpu = xid & fc_cpu_mask;
if (cpu >= nr_cpu_ids || !cpu_possible(cpu)) {
printk_ratelimited(KERN_ERR
"libfc: lookup request for XID = %d, "
"indicates invalid CPU %d\n", xid, cpu);
return NULL;
}
if ((xid >= mp->min_xid) && (xid <= mp->max_xid)) {
pool = per_cpu_ptr(mp->pool, xid & fc_cpu_mask);
pool = per_cpu_ptr(mp->pool, cpu);
spin_lock_bh(&pool->lock);
ep = fc_exch_ptr_get(pool, (xid - mp->min_xid) >> fc_cpu_order);
if (ep) {