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Yonghong Song authored
For jited bpf program, if the subprogram count is 1, i.e., there is no callees in the program, prog->aux->func will be NULL and prog->bpf_func points to image address of the program. If there is more than one subprogram, prog->aux->func is populated, and subprogram 0 can be accessed through either prog->bpf_func or prog->aux->func[0]. Other subprograms should be accessed through prog->aux->func[subprog_id]. This patch fixed a bug in check_attach_btf_id(), where prog->aux->func[subprog_id] is used to access any subprogram which caused a segfault like below: [79162.619208] BUG: kernel NULL pointer dereference, address: 0000000000000000 ...... [79162.634255] Call Trace: [79162.634974] ? _cond_resched+0x15/0x30 [79162.635686] ? kmem_cache_alloc_trace+0x162/0x220 [79162.636398] ? selinux_bpf_prog_alloc+0x1f/0x60 [79162.637111] bpf_prog_load+0x3de/0x690 [79162.637809] __do_sys_bpf+0x105/0x1740 [79162.638488] do_syscall_64+0x5b/0x180 [79162.639147] entry_SYSCALL_64_after_hwframe+0x44/0xa9 ...... Fixes: 5b92a28a ("bpf: Support attaching tracing BPF program to other BPF programs") Reported-by:
Eelco Chaudron <echaudro@redhat.com> Signed-off-by:
Yonghong Song <yhs@fb.com> Signed-off-by:
Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20191205010606.177774-1-yhs@fb.com
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