On Thu, May 12, 2022 at 9:50 AM KP Singh <kpsingh@xxxxxxxxxx> wrote:
>
> +BPF_CALL_5(bpf_getxattr, struct user_namespace *, mnt_userns, struct dentry *,
> + dentry, void *, name, void *, value, size_t, value_size)
> +{
> + return vfs_getxattr(mnt_userns, dentry, name, value, value_size);
> +}
It will deadlock in tracing, since it grabs all kinds of locks
and calls lsm hooks (potentially calling other bpf progs).
It probably should be sleepable only.
Also there is no need to make it uapi.
kfunc is a better interface here.
__vfs_getxattr() is probably better too,
since vfs_getxattr() calls xattr_permission which calls
a bunch of capable*() which will return "random values"
depending on the current task, since it's called from bpf prog.
