From: "Naveen N. Rao" naveen.n.rao@linux.vnet.ibm.com
stable inclusion from stable-v5.10.96 commit ff6bdc205fd0a83bd365405d4e31fb5905826996 bugzilla: https://gitee.com/openeuler/kernel/issues/I55NWB
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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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 Signed-off-by: Yu Liao liaoyu15@huawei.com Reviewed-by: Wei Li liwei391@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- kernel/bpf/stackmap.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 92b38a5da61a..a4c8c584e76b 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -670,13 +670,14 @@ BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf, 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;