bpf: Fix re-attachment branch in bpf_tracing_prog_attach
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.
BUG=b/330305810
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2024-26591 in the Linux kernel.
cos-patch: security-moderate
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>
Change-Id: If83346f53b2ff3b0e0167f1ed221eb2ac3dcd5ba
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/67792
Reviewed-by: Anil Altinay <aaltinay@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index d497459..714969f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2783,6 +2783,10 @@
*
* - 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) {
/*
@@ -2796,6 +2800,11 @@
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);
}
