3.6.11.5 stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Borkmann [ Upstream commit 8da3056c04bfc5f69f840ab038a38389e2de8189 ] 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 Signed-off-by: Steven Rostedt --- net/packet/af_packet.c | 53 +++++++++++++++++++++--------------------------- 1 file changed, 23 insertions(+), 30 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 70f7e18..13dee6a 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -806,36 +806,33 @@ 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(); } /* @@ -926,10 +923,6 @@ 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, -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/