6.1-stable review patch. If anyone has any objections, please let me know.
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From: Jiri Olsa olsajiri@gmail.com
commit 715d82ba636cb3629a6e18a33bb9dbe53f9936ee upstream.
The following case can cause a crash due to missing attach_btf:
1) load rawtp program 2) load fentry program with rawtp as target_fd 3) create tracing link for fentry program with target_fd = 0 4) repeat 3
In the end we have:
- prog->aux->dst_trampoline == NULL - tgt_prog == NULL (because we did not provide target_fd to link_create) - prog->aux->attach_btf == NULL (the program was loaded with attach_prog_fd=X) - the program was loaded for tgt_prog but we have no way to find out which one
BUG: kernel NULL pointer dereference, address: 0000000000000058 Call Trace: <TASK> ? __die+0x20/0x70 ? page_fault_oops+0x15b/0x430 ? fixup_exception+0x22/0x330 ? exc_page_fault+0x6f/0x170 ? asm_exc_page_fault+0x22/0x30 ? bpf_tracing_prog_attach+0x279/0x560 ? btf_obj_id+0x5/0x10 bpf_tracing_prog_attach+0x439/0x560 __sys_bpf+0x1cf4/0x2de0 __x64_sys_bpf+0x1c/0x30 do_syscall_64+0x41/0xf0 entry_SYSCALL_64_after_hwframe+0x6e/0x76
Return -EINVAL in this situation.
Fixes: f3a95075549e0 ("bpf: Allow trampoline re-attach for tracing and lsm programs") Cc: stable@vger.kernel.org Signed-off-by: Jiri Olsa olsajiri@gmail.com Acked-by: Jiri Olsa olsajiri@gmail.com Acked-by: Song Liu song@kernel.org Signed-off-by: Dmitrii Dolgov 9erthalion6@gmail.com Link: https://lore.kernel.org/r/20240103190559.14750-4-9erthalion6@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/bpf/syscall.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3058,6 +3058,10 @@ static int bpf_tracing_prog_attach(struc * * - if prog->aux->dst_trampoline and tgt_prog is NULL, the program * was detached and is going for re-attachment. + * + * - if prog->aux->dst_trampoline is NULL and tgt_prog and prog->aux->attach_btf + * are NULL, then program was already attached and user did not provide + * tgt_prog_fd so we have no way to find out or create trampoline */ if (!prog->aux->dst_trampoline && !tgt_prog) { /* @@ -3071,6 +3075,11 @@ static int bpf_tracing_prog_attach(struc err = -EINVAL; goto out_unlock; } + /* We can allow re-attach only if we have valid attach_btf. */ + if (!prog->aux->attach_btf) { + err = -EINVAL; + goto out_unlock; + } btf_id = prog->aux->attach_btf_id; key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf, btf_id); }