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bc72f3dd89
gcc warns about an uninitialized pointer dereference in the vlan priority handling: net/core/flow_dissector.c: In function '__skb_flow_dissect': net/core/flow_dissector.c:281:61: error: 'vlan' may be used uninitialized in this function [-Werror=maybe-uninitialized] As pointed out by Jiri Pirko, the variable is never actually used without being initialized first as the only way it end up uninitialized is with skb_vlan_tag_present(skb)==true, and that means it does not get accessed. However, the warning hints at some related issues that I'm addressing here: - the second check for the vlan tag is different from the first one that tests the skb for being NULL first, causing both the warning and a possible NULL pointer dereference that was not entirely fixed. - The same patch that introduced the NULL pointer check dropped an earlier optimization that skipped the repeated check of the protocol type - The local '_vlan' variable is referenced through the 'vlan' pointer but the variable has gone out of scope by the time that it is accessed, causing undefined behavior Caching the result of the 'skb && skb_vlan_tag_present(skb)' check in a local variable allows the compiler to further optimize the later check. With those changes, the warning also disappears. Fixes: |
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| .. | ||
| datagram.c | ||
| dev.c | ||
| dev_addr_lists.c | ||
| dev_ioctl.c | ||
| devlink.c | ||
| drop_monitor.c | ||
| dst.c | ||
| dst_cache.c | ||
| ethtool.c | ||
| fib_rules.c | ||
| filter.c | ||
| flow.c | ||
| flow_dissector.c | ||
| gen_estimator.c | ||
| gen_stats.c | ||
| hwbm.c | ||
| link_watch.c | ||
| lwtunnel.c | ||
| Makefile | ||
| neighbour.c | ||
| net-procfs.c | ||
| net-sysfs.c | ||
| net-sysfs.h | ||
| net-traces.c | ||
| net_namespace.c | ||
| netclassid_cgroup.c | ||
| netevent.c | ||
| netpoll.c | ||
| netprio_cgroup.c | ||
| pktgen.c | ||
| ptp_classifier.c | ||
| request_sock.c | ||
| rtnetlink.c | ||
| scm.c | ||
| secure_seq.c | ||
| skbuff.c | ||
| sock.c | ||
| sock_diag.c | ||
| sock_reuseport.c | ||
| stream.c | ||
| sysctl_net_core.c | ||
| timestamping.c | ||
| tso.c | ||
| utils.c | ||