From 8da3056c04bfc5f69f840ab038a38389e2de8189 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Fri, 3 May 2013 02:57:00 +0000 Subject: packet: tpacket_v3: do not trigger bug() on wrong header status Jakub reported that it is fairly easy to trigger the BUG() macro from user space with TPACKET_V3's RX_RING by just giving a wrong header status flag. We already had a similar situation in commit 7f5c3e3a80e6654 (``af_packet: remove BUG statement in tpacket_destruct_skb'') where this was the case in the TX_RING side that could be triggered from user space. So really, don't use BUG() or BUG_ON() unless there's really no way out, and i.e. don't use it for consistency checking when there's user space involved, no excuses, especially not if you're slapping the user with WARN + dump_stack + BUG all at once. The two functions are of concern: prb_retire_current_block() [when block status != TP_STATUS_KERNEL] prb_open_block() [when block_status != TP_STATUS_KERNEL] Calls to prb_open_block() are guarded by ealier checks if block_status is really TP_STATUS_KERNEL (racy!), but the first one BUG() is easily triggable from user space. System behaves still stable after they are removed. Also remove that yoda condition entirely, since it's already guarded. Reported-by: Jakub Zawadzki Signed-off-by: Daniel Borkmann Signed-off-by: David S. Miller --- net/packet/af_packet.c | 53 ++++++++++++++++++++++---------------------------- 1 file changed, 23 insertions(+), 30 deletions(-) (limited to 'net/packet') diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index dd5cd49b0e09..8ec1bca7f859 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -742,36 +742,33 @@ static void prb_open_block(struct tpacket_kbdq_core *pkc1, smp_rmb(); - if (likely(TP_STATUS_KERNEL == BLOCK_STATUS(pbd1))) { + /* We could have just memset this but we will lose the + * flexibility of making the priv area sticky + */ - /* We could have just memset this but we will lose the - * flexibility of making the priv area sticky - */ - BLOCK_SNUM(pbd1) = pkc1->knxt_seq_num++; - BLOCK_NUM_PKTS(pbd1) = 0; - BLOCK_LEN(pbd1) = BLK_PLUS_PRIV(pkc1->blk_sizeof_priv); - getnstimeofday(&ts); - h1->ts_first_pkt.ts_sec = ts.tv_sec; - h1->ts_first_pkt.ts_nsec = ts.tv_nsec; - pkc1->pkblk_start = (char *)pbd1; - pkc1->nxt_offset = pkc1->pkblk_start + BLK_PLUS_PRIV(pkc1->blk_sizeof_priv); - BLOCK_O2FP(pbd1) = (__u32)BLK_PLUS_PRIV(pkc1->blk_sizeof_priv); - BLOCK_O2PRIV(pbd1) = BLK_HDR_LEN; - pbd1->version = pkc1->version; - pkc1->prev = pkc1->nxt_offset; - pkc1->pkblk_end = pkc1->pkblk_start + pkc1->kblk_size; - prb_thaw_queue(pkc1); - _prb_refresh_rx_retire_blk_timer(pkc1); + BLOCK_SNUM(pbd1) = pkc1->knxt_seq_num++; + BLOCK_NUM_PKTS(pbd1) = 0; + BLOCK_LEN(pbd1) = BLK_PLUS_PRIV(pkc1->blk_sizeof_priv); - smp_wmb(); + getnstimeofday(&ts); - return; - } + h1->ts_first_pkt.ts_sec = ts.tv_sec; + h1->ts_first_pkt.ts_nsec = ts.tv_nsec; - WARN(1, "ERROR block:%p is NOT FREE status:%d kactive_blk_num:%d\n", - pbd1, BLOCK_STATUS(pbd1), pkc1->kactive_blk_num); - dump_stack(); - BUG(); + pkc1->pkblk_start = (char *)pbd1; + pkc1->nxt_offset = pkc1->pkblk_start + BLK_PLUS_PRIV(pkc1->blk_sizeof_priv); + + BLOCK_O2FP(pbd1) = (__u32)BLK_PLUS_PRIV(pkc1->blk_sizeof_priv); + BLOCK_O2PRIV(pbd1) = BLK_HDR_LEN; + + pbd1->version = pkc1->version; + pkc1->prev = pkc1->nxt_offset; + pkc1->pkblk_end = pkc1->pkblk_start + pkc1->kblk_size; + + prb_thaw_queue(pkc1); + _prb_refresh_rx_retire_blk_timer(pkc1); + + smp_wmb(); } /* @@ -862,10 +859,6 @@ static void prb_retire_current_block(struct tpacket_kbdq_core *pkc, prb_close_block(pkc, pbd, po, status); return; } - - WARN(1, "ERROR-pbd[%d]:%p\n", pkc->kactive_blk_num, pbd); - dump_stack(); - BUG(); } static int prb_curr_blk_in_use(struct tpacket_kbdq_core *pkc, -- cgit v1.2.3