On Wed, Feb 26, 2025 at 8:00 AM Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > > On Tue, Feb 25, 2025 at 11:06 PM Song Liu <song@xxxxxxxxxx> wrote: > > > > On Tue, Feb 25, 2025 at 4:31 PM Blaise Boscaccy > > <bboscaccy@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > Certain bpf syscall subcommands are available for usage from both > > > userspace and the kernel. LSM modules or eBPF gatekeeper programs may > > > need to take a different course of action depending on whether or not > > > a BPF syscall originated from the kernel or userspace. > > > > > > Additionally, some of the bpf_attr struct fields contain pointers to > > > arbitrary memory. Currently the functionality to determine whether or > > > not a pointer refers to kernel memory or userspace memory is exposed > > > to the bpf verifier, but that information is missing from various LSM > > > hooks. > > > > > > Here we augment the LSM hooks to provide this data, by simply passing > > > the corresponding universal pointer in any hook that contains already > > > contains a bpf_attr struct that corresponds to a subcommand that may > > > be called from the kernel. > > > > I think this information is useful for LSM hooks. > > > > Question: Do we need a full bpfptr_t for these hooks, or just a boolean > > "is_kernel or not"? > > +1 > Just passing the bool should do. > Passing uattr is a footgun. Last thing we need is to open up TOCTOU concerns. Shall we also replace uattr with bool is_kernel in verifier.c? It appears to be a good cleanup. Thanks, Song
