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authorJakub Kicinski <jakub.kicinski@netronome.com>2019-11-04 15:36:57 -0800
committerDavid S. Miller <davem@davemloft.net>2019-11-05 18:07:47 -0800
commit683916f6a84023407761d843048f1aea486b2612 (patch)
tree909645fe5abf23144bbb2687c2216f39a6ed0eba /net
parent57d0f00dfeb3775eae88af1c4aeda6bd35943f20 (diff)
downloadlinux-683916f6a84023407761d843048f1aea486b2612.tar.bz2
net/tls: fix sk_msg trim on fallback to copy mode
sk_msg_trim() tries to only update curr pointer if it falls into the trimmed region. The logic, however, does not take into the account pointer wrapping that sk_msg_iter_var_prev() does nor (as John points out) the fact that msg->sg is a ring buffer. This means that when the message was trimmed completely, the new curr pointer would have the value of MAX_MSG_FRAGS - 1, which is neither smaller than any other value, nor would it actually be correct. Special case the trimming to 0 length a little bit and rework the comparison between curr and end to take into account wrapping. This bug caused the TLS code to not copy all of the message, if zero copy filled in fewer sg entries than memcopy would need. Big thanks to Alexander Potapenko for the non-KMSAN reproducer. v2: - take into account that msg->sg is a ring buffer (John). Link: https://lore.kernel.org/netdev/20191030160542.30295-1-jakub.kicinski@netronome.com/ (v1) Fixes: d829e9c4112b ("tls: convert to generic sk_msg interface") Reported-by: syzbot+f8495bff23a879a6d0bd@syzkaller.appspotmail.com Reported-by: syzbot+6f50c99e8f6194bf363f@syzkaller.appspotmail.com Co-developed-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/core/skmsg.c20
1 files changed, 15 insertions, 5 deletions
diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index cf390e0aa73d..ad31e4e53d0a 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -270,18 +270,28 @@ void sk_msg_trim(struct sock *sk, struct sk_msg *msg, int len)
msg->sg.data[i].length -= trim;
sk_mem_uncharge(sk, trim);
+ /* Adjust copybreak if it falls into the trimmed part of last buf */
+ if (msg->sg.curr == i && msg->sg.copybreak > msg->sg.data[i].length)
+ msg->sg.copybreak = msg->sg.data[i].length;
out:
- /* If we trim data before curr pointer update copybreak and current
- * so that any future copy operations start at new copy location.
+ sk_msg_iter_var_next(i);
+ msg->sg.end = i;
+
+ /* If we trim data a full sg elem before curr pointer update
+ * copybreak and current so that any future copy operations
+ * start at new copy location.
* However trimed data that has not yet been used in a copy op
* does not require an update.
*/
- if (msg->sg.curr >= i) {
+ if (!msg->sg.size) {
+ msg->sg.curr = msg->sg.start;
+ msg->sg.copybreak = 0;
+ } else if (sk_msg_iter_dist(msg->sg.start, msg->sg.curr) >=
+ sk_msg_iter_dist(msg->sg.start, msg->sg.end)) {
+ sk_msg_iter_var_prev(i);
msg->sg.curr = i;
msg->sg.copybreak = msg->sg.data[i].length;
}
- sk_msg_iter_var_next(i);
- msg->sg.end = i;
}
EXPORT_SYMBOL_GPL(sk_msg_trim);