From: Naveen N. Rao naveen.n.rao@linux.vnet.ibm.com
commit b992f01e66150fc5e90be4a96f5eb8e634c8249e upstream.
task_pt_regs() can return NULL on powerpc for kernel threads. This is then used in __bpf_get_stack() to check for user mode, resulting in a kernel oops. Guard against this by checking return value of task_pt_regs() before trying to obtain the call chain.
Fixes: fa28dcb82a38f8 ("bpf: Introduce helper bpf_get_task_stack()") Cc: stable@vger.kernel.org # v5.9+ Signed-off-by: Naveen N. Rao naveen.n.rao@linux.vnet.ibm.com Acked-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/d5ef83c361cc255494afd15ff1b4fb02a36e1dcf.164146812... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/bpf/stackmap.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -664,13 +664,14 @@ BPF_CALL_4(bpf_get_task_stack, struct ta u32, size, u64, flags) { struct pt_regs *regs; - long res; + long res = -EINVAL;
if (!try_get_task_stack(task)) return -EFAULT;
regs = task_pt_regs(task); - res = __bpf_get_stack(regs, task, NULL, buf, size, flags); + if (regs) + res = __bpf_get_stack(regs, task, NULL, buf, size, flags); put_task_stack(task);
return res;