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batman-adv: fix broken double-free backport leading to frequent crashes

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NeoRaider committed Mar 28, 2017
1 parent 6cbd658 commit d452a7c2cf1c0da4e034666a50dc0e7aa9ddc592
@@ -0,0 +1,51 @@
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Tue, 28 Mar 2017 14:39:48 +0200
Subject: batman-adv: Fix double free during fragment merge error
diff --git a/batman-adv/patches/1003-batman-adv-Fix-double-free-during-fragment-merge-err.patch b/batman-adv/patches/1003-batman-adv-Fix-double-free-during-fragment-merge-err.patch
new file mode 100644
index 0000000000000000000000000000000000000000..42748aac79d082e67a8552690b3aa6e7f5ec7d12
--- /dev/null
+++ b/batman-adv/patches/1003-batman-adv-Fix-double-free-during-fragment-merge-err.patch
@@ -0,0 +1,41 @@
+From ee1415285ddb56a3c15b5b70d7b403637486382c Mon Sep 17 00:00:00 2001
+Message-Id: <ee1415285ddb56a3c15b5b70d7b403637486382c.1490704674.git.mschiffer@universe-factory.net>
+From: Matthias Schiffer <mschiffer@universe-factory.net>
+Date: Tue, 28 Mar 2017 14:35:12 +0200
+Subject: [PATCH] batman-adv: Fix double free during fragment merge error
+
+The function batadv_frag_skb_buffer was supposed not to consume the skbuff
+on errors. This was followed in the helper function
+batadv_frag_insert_packet when the skb would potentially be inserted in the
+fragment queue. But it could happen that the next helper function
+batadv_frag_merge_packets would try to merge the fragments and fail. This
+results in a kfree_skb of all the enqueued fragments (including the just
+inserted one). batadv_recv_frag_packet would detect the error in
+batadv_frag_skb_buffer and try to free the skb again.
+
+The behavior of batadv_frag_skb_buffer must therefore be changed to return
+true when batadv_frag_merge_packets fails.
+
+Fixes: 9b3eab61754d ("batman-adv: Receive fragmented packets and merge")
+Signed-off-by: Sven Eckelmann <sven@narfation.org>
+[Matthias Schiffer: backport to batman-adv 2016.2]
+---
+ net/batman-adv/fragmentation.c | 2 --
+ 1 file changed, 2 deletions(-)
+
+diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
+index 65536db1..21e5b79f 100644
+--- a/net/batman-adv/fragmentation.c
++++ b/net/batman-adv/fragmentation.c
+@@ -326,8 +326,6 @@ bool batadv_frag_skb_buffer(struct sk_buff **skb,
+ goto out;
+
+ skb_out = batadv_frag_merge_packets(&head);
+- if (!skb_out)
+- goto out_err;
+
+ out:
+ *skb = skb_out;
+--
+2.12.1
+
@@ -1,80 +1,7 @@
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Thu, 9 Mar 2017 19:00:12 +0100
Subject: batman-adv: backport a few maint patches
Date: Tue, 28 Mar 2017 14:40:20 +0200
Subject: batman-adv: Keep fragments equally sized
In particular, this fixes packages of a certain range of sizes not being
transmitted correctly, leading to hanging TCP connections.
diff --git a/batman-adv/patches/1003-batman-adv-Fix-double-free-during-fragment-merge-err.patch b/batman-adv/patches/1003-batman-adv-Fix-double-free-during-fragment-merge-err.patch
new file mode 100644
index 0000000000000000000000000000000000000000..4d754ecda1451b5c3e25f74da97fab18b7a93c87
--- /dev/null
+++ b/batman-adv/patches/1003-batman-adv-Fix-double-free-during-fragment-merge-err.patch
@@ -0,0 +1,64 @@
+From bcb7b6149bd9d1f41dae01ab47e74b8a931a650f Mon Sep 17 00:00:00 2001
+Message-Id: <bcb7b6149bd9d1f41dae01ab47e74b8a931a650f.1489082249.git.mschiffer@universe-factory.net>
+From: Sven Eckelmann <sven@narfation.org>
+Date: Sun, 12 Feb 2017 11:26:33 +0100
+Subject: [PATCH] batman-adv: Fix double free during fragment merge error
+
+The function batadv_frag_skb_buffer was supposed not to consume the skbuff
+on errors. This was followed in the helper function
+batadv_frag_insert_packet when the skb would potentially be inserted in the
+fragment queue. But it could happen that the next helper function
+batadv_frag_merge_packets would try to merge the fragments and fail. This
+results in a kfree_skb of all the enqueued fragments (including the just
+inserted one). batadv_recv_frag_packet would detect the error in
+batadv_frag_skb_buffer and try to free the skb again.
+
+The behavior of batadv_frag_skb_buffer (and its helper
+batadv_frag_insert_packet) must therefore be changed to always consume the
+skbuff to have a common behavior and avoid the double kfree_skb.
+
+Fixes: 9b3eab61754d ("batman-adv: Receive fragmented packets and merge")
+Signed-off-by: Sven Eckelmann <sven@narfation.org>
+---
+ net/batman-adv/fragmentation.c | 8 +++++---
+ 1 file changed, 5 insertions(+), 3 deletions(-)
+
+diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
+index 65536db1..c3e293a3 100644
+--- a/net/batman-adv/fragmentation.c
++++ b/net/batman-adv/fragmentation.c
+@@ -233,8 +233,10 @@ err_unlock:
+ spin_unlock_bh(&chain->lock);
+
+ err:
+- if (!ret)
++ if (!ret) {
+ kfree(frag_entry_new);
++ kfree_skb(skb);
++ }
+
+ return ret;
+ }
+@@ -305,7 +307,7 @@ free:
+ *
+ * There are three possible outcomes: 1) Packet is merged: Return true and
+ * set *skb to merged packet; 2) Packet is buffered: Return true and set *skb
+- * to NULL; 3) Error: Return false and leave skb as is.
++ * to NULL; 3) Error: Return false and free skb.
+ *
+ * Return: true when packet is merged or buffered, false when skb is not not
+ * used.
+@@ -330,9 +332,9 @@ bool batadv_frag_skb_buffer(struct sk_buff **skb,
+ goto out_err;
+
+ out:
+- *skb = skb_out;
+ ret = true;
+ out_err:
++ *skb = skb_out;
+ return ret;
+ }
+
+--
+2.12.0
+
diff --git a/batman-adv/patches/1004-batman-adv-Keep-fragments-equally-sized.patch b/batman-adv/patches/1004-batman-adv-Keep-fragments-equally-sized.patch
new file mode 100644
index 0000000000000000000000000000000000000000..431c0b4a1a722c4c2ebae390bc0c90be18966023

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