generic: workaround arptables arpt_arp structure padding issue (#14577)
Linaro GCC 4.6-2013.05 incorrectly pads the arpt_arp structure on at least the ar71xx target, resulting in a two bytes shorter struct in the kernel compared to what arptables userspace expects. When comparing sizeof(struct arpt_arp) in kernel and userspace, the former yields 162 byte, while the latter is 164 byte. As a consequence, the subsequent target_offset and next_offset members of the parent arpt_entry structure contain invalid values when processed by the arptables binary, leading to bad memory accesses in the populate_cache() procedure, subsequently causing a segfault. Signed-off-by: Jo-Philipp Wich <jow@openwrt.org> SVN-Revision: 38999master
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@ -0,0 +1,16 @@ |
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--- a/include/uapi/linux/netfilter_arp/arp_tables.h
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+++ b/include/uapi/linux/netfilter_arp/arp_tables.h
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@@ -68,6 +68,13 @@ struct arpt_arp {
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__u8 flags;
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/* Inverse flags */
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__u16 invflags;
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+
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+ /* For some reason Linaro GCC 4.6-2013.05 omits the two
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+ * byte padding here when building for MIPS 34kc, leading to
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+ * userspace abi mismatches.
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+ * Add a dummy field to align this struct to 4 bytes
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+ */
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+ __u16 padding;
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};
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/* Values for "flag" field in struct arpt_ip (general arp structure).
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