From 031097d9e079e40dce401031d1012e83d80eaf01 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Wed, 27 Nov 2019 12:16:41 -0800 Subject: net: skmsg: fix TLS 1.3 crash with full sk_msg TLS 1.3 started using the entry at the end of the SG array for chaining-in the single byte content type entry. This mostly works: [ E E E E E E . . ] ^ ^ start end E < content type / [ E E E E E E C . ] ^ ^ start end (Where E denotes a populated SG entry; C denotes a chaining entry.) If the array is full, however, the end will point to the start: [ E E E E E E E E ] ^ start end And we end up overwriting the start: E < content type / [ C E E E E E E E ] ^ start end The sg array is supposed to be a circular buffer with start and end markers pointing anywhere. In case where start > end (i.e. the circular buffer has "wrapped") there is an extra entry reserved at the end to chain the two halves together. [ E E E E E E . . l ] (Where l is the reserved entry for "looping" back to front. As suggested by John, let's reserve another entry for chaining SG entries after the main circular buffer. Note that this entry has to be pointed to by the end entry so its position is not fixed. Examples of full messages: [ E E E E E E E E . l ] ^ ^ start end <---------------. [ E E . E E E E E E l ] ^ ^ end start Now the end will always point to an unused entry, so TLS 1.3 can always use it. Fixes: 130b392c6cd6 ("net: tls: Add tls 1.3 support") Signed-off-by: Jakub Kicinski Reviewed-by: Simon Horman Signed-off-by: David S. Miller --- net/core/filter.c | 8 ++++---- net/core/skmsg.c | 2 +- 2 files changed, 5 insertions(+), 5 deletions(-) (limited to 'net/core') diff --git a/net/core/filter.c b/net/core/filter.c index b0ed048585ba..f1e703eed3d2 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2299,7 +2299,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start, WARN_ON_ONCE(last_sge == first_sge); shift = last_sge > first_sge ? last_sge - first_sge - 1 : - MAX_SKB_FRAGS - first_sge + last_sge - 1; + NR_MSG_FRAG_IDS - first_sge + last_sge - 1; if (!shift) goto out; @@ -2308,8 +2308,8 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start, do { u32 move_from; - if (i + shift >= MAX_MSG_FRAGS) - move_from = i + shift - MAX_MSG_FRAGS; + if (i + shift >= NR_MSG_FRAG_IDS) + move_from = i + shift - NR_MSG_FRAG_IDS; else move_from = i + shift; if (move_from == msg->sg.end) @@ -2323,7 +2323,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start, } while (1); msg->sg.end = msg->sg.end - shift > msg->sg.end ? - msg->sg.end - shift + MAX_MSG_FRAGS : + msg->sg.end - shift + NR_MSG_FRAG_IDS : msg->sg.end - shift; out: msg->data = sg_virt(&msg->sg.data[first_sge]) + start - offset; diff --git a/net/core/skmsg.c b/net/core/skmsg.c index a469d2124f3f..ded2d5227678 100644 --- a/net/core/skmsg.c +++ b/net/core/skmsg.c @@ -421,7 +421,7 @@ static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *skb) copied = skb->len; msg->sg.start = 0; msg->sg.size = copied; - msg->sg.end = num_sge == MAX_MSG_FRAGS ? 0 : num_sge; + msg->sg.end = num_sge; msg->skb = skb; sk_psock_queue_msg(psock, msg); -- cgit v1.2.3-59-g8ed1b