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authorJiri Wiesner <jwiesner@suse.com>2018-12-05 16:55:29 +0100
committerDavid S. Miller <davem@davemloft.net>2018-12-05 20:44:46 -0800
commitebaf39e6032faf77218220707fc3fa22487784e0 (patch)
tree1ff6b562ec031ef925841174a9ed9a41b4e2fef0 /net/ipv4/ip_fragment.c
parentsctp: frag_point sanity check (diff)
downloadlinux-dev-ebaf39e6032faf77218220707fc3fa22487784e0.tar.xz
linux-dev-ebaf39e6032faf77218220707fc3fa22487784e0.zip
ipv4: ipv6: netfilter: Adjust the frag mem limit when truesize changes
The *_frag_reasm() functions are susceptible to miscalculating the byte count of packet fragments in case the truesize of a head buffer changes. The truesize member may be changed by the call to skb_unclone(), leaving the fragment memory limit counter unbalanced even if all fragments are processed. This miscalculation goes unnoticed as long as the network namespace which holds the counter is not destroyed. Should an attempt be made to destroy a network namespace that holds an unbalanced fragment memory limit counter the cleanup of the namespace never finishes. The thread handling the cleanup gets stuck in inet_frags_exit_net() waiting for the percpu counter to reach zero. The thread is usually in running state with a stacktrace similar to: PID: 1073 TASK: ffff880626711440 CPU: 1 COMMAND: "kworker/u48:4" #5 [ffff880621563d48] _raw_spin_lock at ffffffff815f5480 #6 [ffff880621563d48] inet_evict_bucket at ffffffff8158020b #7 [ffff880621563d80] inet_frags_exit_net at ffffffff8158051c #8 [ffff880621563db0] ops_exit_list at ffffffff814f5856 #9 [ffff880621563dd8] cleanup_net at ffffffff814f67c0 #10 [ffff880621563e38] process_one_work at ffffffff81096f14 It is not possible to create new network namespaces, and processes that call unshare() end up being stuck in uninterruptible sleep state waiting to acquire the net_mutex. The bug was observed in the IPv6 netfilter code by Per Sundstrom. I thank him for his analysis of the problem. The parts of this patch that apply to IPv4 and IPv6 fragment reassembly are preemptive measures. Signed-off-by: Jiri Wiesner <jwiesner@suse.com> Reported-by: Per Sundstrom <per.sundstrom@redqube.se> Acked-by: Peter Oskolkov <posk@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to '')
-rw-r--r--net/ipv4/ip_fragment.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index d6ee343fdb86..aa0b22697998 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -515,6 +515,7 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
struct rb_node *rbn;
int len;
int ihlen;
+ int delta;
int err;
u8 ecn;
@@ -556,10 +557,16 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
if (len > 65535)
goto out_oversize;
+ delta = - head->truesize;
+
/* Head of list must not be cloned. */
if (skb_unclone(head, GFP_ATOMIC))
goto out_nomem;
+ delta += head->truesize;
+ if (delta)
+ add_frag_mem_limit(qp->q.net, delta);
+
/* If the first fragment is fragmented itself, we split
* it to two chunks: the first with data and paged part
* and the second, holding only fragments. */