kernel.git/kernel/bpf/helpers.c, branch linux-5.18.y

bpf: Allow storing referenced kptr in map

2022-08-17T12:41:08Z

[ Upstream commit c0a5a21c25f37c9fd7b36072f9968cdff1e4aa13 ] Extending the code in previous commits, introduce referenced kptr support, which needs to be tagged using 'kptr_ref' tag instead. Unlike unreferenced kptr, referenced kptr have a lot more restrictions. In addition to the type matching, only a newly introduced bpf_kptr_xchg helper is allowed to modify the map value at that offset. This transfers the referenced pointer being stored into the map, releasing the references state for the program, and returning the old value and creating new reference state for the returned pointer. Similar to unreferenced pointer case, return value for this case will also be PTR_TO_BTF_ID_OR_NULL. The reference for the returned pointer must either be eventually released by calling the corresponding release function, otherwise it must be transferred into another map. It is also allowed to call bpf_kptr_xchg with a NULL pointer, to clear the value, and obtain the old value if any. BPF_LDX, BPF_STX, and BPF_ST cannot access referenced kptr. A future commit will permit using BPF_LDX for such pointers, but attempt at making it safe, since the lifetime of object won't be guaranteed. There are valid reasons to enforce the restriction of permitting only bpf_kptr_xchg to operate on referenced kptr. The pointer value must be consistent in face of concurrent modification, and any prior values contained in the map must also be released before a new one is moved into the map. To ensure proper transfer of this ownership, bpf_kptr_xchg returns the old value, which the verifier would require the user to either free or move into another map, and releases the reference held for the pointer being moved in. In the future, direct BPF_XCHG instruction may also be permitted to work like bpf_kptr_xchg helper. Note that process_kptr_func doesn't have to call check_helper_mem_access, since we already disallow rdonly/wronly flags for map, which is what check_map_access_type checks, and we already ensure the PTR_TO_MAP_VALUE refers to kptr by obtaining its off_desc, so check_map_access is also not required. Signed-off-by: Kumar Kartikeya Dwivedi Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20220424214901.2743946-4-memxor@gmail.com Signed-off-by: Sasha Levin

bpf: Replace strncpy() with strscpy()

2022-03-08T06:04:33Z

Using strncpy() on NUL-terminated strings is considered deprecated[1]. Moreover, if the length of 'task->comm' is less than the destination buffer size, strncpy() will NUL-pad the destination buffer, which is a needless performance penalty. Replacing strncpy() with strscpy() fixes all these issues. [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings Signed-off-by: Yuntao Wang Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20220304070408.233658-1-ytcoode@gmail.com

bpf: Cleanup comments

2022-02-23T23:17:51Z

Add leading space to spdx tag Use // for spdx c file comment Replacements resereved to reserved inbetween to in between everytime to every time intutivie to intuitive currenct to current encontered to encountered referenceing to referencing upto to up to exectuted to executed Signed-off-by: Tom Rix Signed-off-by: Andrii Nakryiko Acked-by: Song Liu Link: https://lore.kernel.org/bpf/20220220184055.3608317-1-trix@redhat.com

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2022-02-17T20:22:28Z

Fast path bpf marge for some -next work. Signed-off-by: Jakub Kicinski

bpf: Emit bpf_timer in vmlinux BTF

2022-02-11T21:21:47Z

Currently the following code in check_and_init_map_value() *(struct bpf_timer *)(dst + map->timer_off) = (struct bpf_timer){}; can help generate bpf_timer definition in vmlinuxBTF. But the code above may not zero the whole structure due to anonymour members and that code will be replaced by memset in the subsequent patch and bpf_timer definition will disappear from vmlinuxBTF. Let us emit the type explicitly so bpf program can continue to use it from vmlinux.h. Signed-off-by: Yonghong Song Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20220211194948.3141529-1-yhs@fb.com

bpf: make bpf_copy_from_user_task() gpl only

2022-01-31T20:44:37Z

access_process_vm() is exported by EXPORT_SYMBOL_GPL(). Signed-off-by: Kenta Tada Link: https://lore.kernel.org/r/20220128170906.21154-1-Kenta.Tada@sony.com Signed-off-by: Alexei Starovoitov

bpf: Add bpf_copy_from_user_task() helper

2022-01-25T03:59:27Z

This adds a helper for bpf programs to read the memory of other tasks. As an example use case at Meta, we are using a bpf task iterator program and this new helper to print C++ async stack traces for all threads of a given process. Signed-off-by: Kenny Yu Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20220124185403.468466-3-kennyyu@fb.com Signed-off-by: Alexei Starovoitov

bpf: Add MEM_RDONLY for helper args that are pointers to rdonly mem.

2021-12-18T21:27:41Z

Some helper functions may modify its arguments, for example, bpf_d_path, bpf_get_stack etc. Previously, their argument types were marked as ARG_PTR_TO_MEM, which is compatible with read-only mem types, such as PTR_TO_RDONLY_BUF. Therefore it's legitimate, but technically incorrect, to modify a read-only memory by passing it into one of such helper functions. This patch tags the bpf_args compatible with immutable memory with MEM_RDONLY flag. The arguments that don't have this flag will be only compatible with mutable memory types, preventing the helper from modifying a read-only memory. The bpf_args that have MEM_RDONLY are compatible with both mutable memory and immutable memory. Signed-off-by: Hao Luo Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20211217003152.48334-9-haoluo@google.com

bpf: Make per_cpu_ptr return rdonly PTR_TO_MEM.

2021-12-18T21:27:41Z

Tag the return type of {per, this}_cpu_ptr with RDONLY_MEM. The returned value of this pair of helpers is kernel object, which can not be updated by bpf programs. Previously these two helpers return PTR_OT_MEM for kernel objects of scalar type, which allows one to directly modify the memory. Now with RDONLY_MEM tagging, the verifier will reject programs that write into RDONLY_MEM. Fixes: 63d9b80dcf2c ("bpf: Introducte bpf_this_cpu_ptr()") Fixes: eaa6bcb71ef6 ("bpf: Introduce bpf_per_cpu_ptr()") Fixes: 4976b718c355 ("bpf: Introduce pseudo_btf_id") Signed-off-by: Hao Luo Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20211217003152.48334-8-haoluo@google.com

bpf: Replace RET_XXX_OR_NULL with RET_XXX | PTR_MAYBE_NULL

2021-12-18T20:48:08Z

We have introduced a new type to make bpf_ret composable, by reserving high bits to represent flags. One of the flag is PTR_MAYBE_NULL, which indicates a pointer may be NULL. When applying this flag to ret_types, it means the returned value could be a NULL pointer. This patch switches the qualified arg_types to use this flag. The ret_types changed in this patch include: 1. RET_PTR_TO_MAP_VALUE_OR_NULL 2. RET_PTR_TO_SOCKET_OR_NULL 3. RET_PTR_TO_TCP_SOCK_OR_NULL 4. RET_PTR_TO_SOCK_COMMON_OR_NULL 5. RET_PTR_TO_ALLOC_MEM_OR_NULL 6. RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL 7. RET_PTR_TO_BTF_ID_OR_NULL This patch doesn't eliminate the use of these names, instead it makes them aliases to 'RET_PTR_TO_XXX | PTR_MAYBE_NULL'. Signed-off-by: Hao Luo Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20211217003152.48334-4-haoluo@google.com