fs/bpf_fs_kfuncs.c | 34 ++++ fs/kernfs/inode.c | 74 ++++---- kernel/bpf/helpers.c | 3 + kernel/bpf/verifier.c | 5 + .../testing/selftests/bpf/bpf_experimental.h | 3 + .../selftests/bpf/prog_tests/cgroup_xattr.c | 145 ++++++++++++++++ .../selftests/bpf/progs/cgroup_read_xattr.c | 158 ++++++++++++++++++ .../selftests/bpf/progs/read_cgroupfs_xattr.c | 60 +++++++ 8 files changed, 448 insertions(+), 34 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/cgroup_xattr.c create mode 100644 tools/testing/selftests/bpf/progs/cgroup_read_xattr.c create mode 100644 tools/testing/selftests/bpf/progs/read_cgroupfs_xattr.c
Introduce a new kfunc bpf_cgroup_read_xattr, which can read xattr from cgroupfs nodes. The primary users are LSMs, cgroup programs, and sched_ext. --- Changes v2 => v3: 1. Make bpf_cgroup_read_xattr available to all program types. 2. Fix gcc build warning on the selftests. 3. Add "ifdef CONFIG_CGROUPS" around bpf_cgroup_read_xattr. v2: https://lore.kernel.org/bpf/20250619220114.3956120-1-song@kernel.org/ Changes v1 => v2: 1. Replace 1/4 in v1 with Chritian's version (1/5 in v2). 2. Rename bpf_kernfs_read_xattr => bpf_cgroup_read_xattr, and limit access to cgroup only. 3. Add 5/5, which makes bpf_cgroup_read_xattr available to cgroup and struct_ops programs. v1: https://lore.kernel.org/bpf/20250618233739.189106-1-song@kernel.org/ Christian Brauner (1): kernfs: remove iattr_mutex Song Liu (3): bpf: Introduce bpf_cgroup_read_xattr to read xattr of cgroup's node bpf: Mark cgroup_subsys_state->cgroup RCU safe selftests/bpf: Add tests for bpf_cgroup_read_xattr fs/bpf_fs_kfuncs.c | 34 ++++ fs/kernfs/inode.c | 74 ++++---- kernel/bpf/helpers.c | 3 + kernel/bpf/verifier.c | 5 + .../testing/selftests/bpf/bpf_experimental.h | 3 + .../selftests/bpf/prog_tests/cgroup_xattr.c | 145 ++++++++++++++++ .../selftests/bpf/progs/cgroup_read_xattr.c | 158 ++++++++++++++++++ .../selftests/bpf/progs/read_cgroupfs_xattr.c | 60 +++++++ 8 files changed, 448 insertions(+), 34 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/cgroup_xattr.c create mode 100644 tools/testing/selftests/bpf/progs/cgroup_read_xattr.c create mode 100644 tools/testing/selftests/bpf/progs/read_cgroupfs_xattr.c -- 2.47.1
On Sun, 22 Jun 2025 23:38:50 -0700, Song Liu wrote:
> Introduce a new kfunc bpf_cgroup_read_xattr, which can read xattr from
> cgroupfs nodes. The primary users are LSMs, cgroup programs, and sched_ext.
>
Applied to the vfs-6.17.bpf branch of the vfs/vfs.git tree.
Patches in the vfs-6.17.bpf branch should appear in linux-next soon.
Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.
It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.
Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.
tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs-6.17.bpf
[1/4] kernfs: remove iattr_mutex
https://git.kernel.org/vfs/vfs/c/d1f4e9026007
[2/4] bpf: Introduce bpf_cgroup_read_xattr to read xattr of cgroup's node
https://git.kernel.org/vfs/vfs/c/535b070f4a80
[3/4] bpf: Mark cgroup_subsys_state->cgroup RCU safe
https://git.kernel.org/vfs/vfs/c/1504d8c7c702
[4/4] selftests/bpf: Add tests for bpf_cgroup_read_xattr
https://git.kernel.org/vfs/vfs/c/f4fba2d6d282
On Mon, Jun 23, 2025 at 4:03 AM Christian Brauner <brauner@kernel.org> wrote: > > On Sun, 22 Jun 2025 23:38:50 -0700, Song Liu wrote: > > Introduce a new kfunc bpf_cgroup_read_xattr, which can read xattr from > > cgroupfs nodes. The primary users are LSMs, cgroup programs, and sched_ext. > > > > Applied to the vfs-6.17.bpf branch of the vfs/vfs.git tree. > Patches in the vfs-6.17.bpf branch should appear in linux-next soon. Thanks. Now merged into bpf-next/master as well. > Please report any outstanding bugs that were missed during review in a > new review to the original patch series allowing us to drop it. bugs :( > It's encouraged to provide Acked-bys and Reviewed-bys even though the > patch has now been applied. If possible patch trailers will be updated. Pls don't. Keep it as-is, otherwise there will be merge conflicts during the merge window. > Note that commit hashes shown below are subject to change due to rebase, > trailer updates or similar. If in doubt, please check the listed branch. > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git > branch: vfs-6.17.bpf > > [1/4] kernfs: remove iattr_mutex > https://git.kernel.org/vfs/vfs/c/d1f4e9026007 > [2/4] bpf: Introduce bpf_cgroup_read_xattr to read xattr of cgroup's node > https://git.kernel.org/vfs/vfs/c/535b070f4a80 > [3/4] bpf: Mark cgroup_subsys_state->cgroup RCU safe > https://git.kernel.org/vfs/vfs/c/1504d8c7c702 > [4/4] selftests/bpf: Add tests for bpf_cgroup_read_xattr > https://git.kernel.org/vfs/vfs/c/f4fba2d6d282 Something wrong with this selftest. Cleanup is not done correctly. ./test_progs -t lsm_cgroup Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED ./test_progs -t lsm_cgroup Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED ./test_progs -t cgroup_xattr Summary: 1/8 PASSED, 0 SKIPPED, 0 FAILED ./test_progs -t lsm_cgroup test_lsm_cgroup_functional:PASS:bind(ETH_P_ALL) 0 nsec (network_helpers.c:121: errno: Cannot assign requested address) Failed to bind socket test_lsm_cgroup_functional:FAIL:start_server unexpected start_server: actual -1 < expected 0 (network_helpers.c:360: errno: Bad file descriptor) getsockopt(SOL_PROTOCOL) test_lsm_cgroup_functional:FAIL:connect_to_fd unexpected connect_to_fd: actual -1 < expected 0 test_lsm_cgroup_functional:FAIL:accept unexpected accept: actual -1 < expected 0 test_lsm_cgroup_functional:FAIL:getsockopt unexpected getsockopt: actual -1 < expected 0 test_lsm_cgroup_functional:FAIL:sk_priority unexpected sk_priority: actual 0 != expected 234 ... Summary: 0/1 PASSED, 0 SKIPPED, 1 FAILED Song, Please follow up with the fix for selftest. It will be in bpf-next only.
On Thu, Jun 26, 2025 at 07:14:20PM -0700, Alexei Starovoitov wrote: > On Mon, Jun 23, 2025 at 4:03 AM Christian Brauner <brauner@kernel.org> wrote: > > > > On Sun, 22 Jun 2025 23:38:50 -0700, Song Liu wrote: > > > Introduce a new kfunc bpf_cgroup_read_xattr, which can read xattr from > > > cgroupfs nodes. The primary users are LSMs, cgroup programs, and sched_ext. > > > > > > > Applied to the vfs-6.17.bpf branch of the vfs/vfs.git tree. > > Patches in the vfs-6.17.bpf branch should appear in linux-next soon. > > Thanks. > Now merged into bpf-next/master as well. > > > Please report any outstanding bugs that were missed during review in a > > new review to the original patch series allowing us to drop it. > > bugs :( > > > It's encouraged to provide Acked-bys and Reviewed-bys even though the > > patch has now been applied. If possible patch trailers will be updated. > > Pls don't. Keep it as-is, otherwise there will be merge conflicts > during the merge window. This is just the common blurb. As soon as another part of the tree relies on something we stabilize the branch and only do fixes on top and never rebase. We usually recommend just pulling the branch which I think you did. > > > Note that commit hashes shown below are subject to change due to rebase, > > trailer updates or similar. If in doubt, please check the listed branch. > > > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git > > branch: vfs-6.17.bpf > > > > [1/4] kernfs: remove iattr_mutex > > https://git.kernel.org/vfs/vfs/c/d1f4e9026007 > > [2/4] bpf: Introduce bpf_cgroup_read_xattr to read xattr of cgroup's node > > https://git.kernel.org/vfs/vfs/c/535b070f4a80 > > [3/4] bpf: Mark cgroup_subsys_state->cgroup RCU safe > > https://git.kernel.org/vfs/vfs/c/1504d8c7c702 > > [4/4] selftests/bpf: Add tests for bpf_cgroup_read_xattr > > https://git.kernel.org/vfs/vfs/c/f4fba2d6d282 > > Something wrong with this selftest. > Cleanup is not done correctly. > > ./test_progs -t lsm_cgroup > Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED > ./test_progs -t lsm_cgroup > Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED > ./test_progs -t cgroup_xattr > Summary: 1/8 PASSED, 0 SKIPPED, 0 FAILED > ./test_progs -t lsm_cgroup > test_lsm_cgroup_functional:PASS:bind(ETH_P_ALL) 0 nsec > (network_helpers.c:121: errno: Cannot assign requested address) Failed > to bind socket > test_lsm_cgroup_functional:FAIL:start_server unexpected start_server: > actual -1 < expected 0 > (network_helpers.c:360: errno: Bad file descriptor) getsockopt(SOL_PROTOCOL) > test_lsm_cgroup_functional:FAIL:connect_to_fd unexpected > connect_to_fd: actual -1 < expected 0 > test_lsm_cgroup_functional:FAIL:accept unexpected accept: actual -1 < expected 0 > test_lsm_cgroup_functional:FAIL:getsockopt unexpected getsockopt: > actual -1 < expected 0 > test_lsm_cgroup_functional:FAIL:sk_priority unexpected sk_priority: > actual 0 != expected 234 > ... > Summary: 0/1 PASSED, 0 SKIPPED, 1 FAILED > > > Song, > Please follow up with the fix for selftest. > It will be in bpf-next only. We should put that commit on the shared vfs-6.17.bpf branch.
On Tue, Jul 1, 2025 at 1:32 AM Christian Brauner <brauner@kernel.org> wrote: > > On Thu, Jun 26, 2025 at 07:14:20PM -0700, Alexei Starovoitov wrote: > > On Mon, Jun 23, 2025 at 4:03 AM Christian Brauner <brauner@kernel.org> wrote: > > > > > > On Sun, 22 Jun 2025 23:38:50 -0700, Song Liu wrote: > > > > Introduce a new kfunc bpf_cgroup_read_xattr, which can read xattr from > > > > cgroupfs nodes. The primary users are LSMs, cgroup programs, and sched_ext. > > > > > > > > > > Applied to the vfs-6.17.bpf branch of the vfs/vfs.git tree. > > > Patches in the vfs-6.17.bpf branch should appear in linux-next soon. > > > > Thanks. > > Now merged into bpf-next/master as well. > > > > > Please report any outstanding bugs that were missed during review in a > > > new review to the original patch series allowing us to drop it. > > > > bugs :( > > > > > It's encouraged to provide Acked-bys and Reviewed-bys even though the > > > patch has now been applied. If possible patch trailers will be updated. > > > > Pls don't. Keep it as-is, otherwise there will be merge conflicts > > during the merge window. > > This is just the common blurb. As soon as another part of the tree > relies on something we stabilize the branch and only do fixes on top and > never rebase. We usually recommend just pulling the branch which I think > you did. > > > > > > Note that commit hashes shown below are subject to change due to rebase, > > > trailer updates or similar. If in doubt, please check the listed branch. > > > > > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git > > > branch: vfs-6.17.bpf > > > > > > [1/4] kernfs: remove iattr_mutex > > > https://git.kernel.org/vfs/vfs/c/d1f4e9026007 > > > [2/4] bpf: Introduce bpf_cgroup_read_xattr to read xattr of cgroup's node > > > https://git.kernel.org/vfs/vfs/c/535b070f4a80 > > > [3/4] bpf: Mark cgroup_subsys_state->cgroup RCU safe > > > https://git.kernel.org/vfs/vfs/c/1504d8c7c702 > > > [4/4] selftests/bpf: Add tests for bpf_cgroup_read_xattr > > > https://git.kernel.org/vfs/vfs/c/f4fba2d6d282 > > > > Something wrong with this selftest. > > Cleanup is not done correctly. > > > > ./test_progs -t lsm_cgroup > > Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED > > ./test_progs -t lsm_cgroup > > Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED > > ./test_progs -t cgroup_xattr > > Summary: 1/8 PASSED, 0 SKIPPED, 0 FAILED > > ./test_progs -t lsm_cgroup > > test_lsm_cgroup_functional:PASS:bind(ETH_P_ALL) 0 nsec > > (network_helpers.c:121: errno: Cannot assign requested address) Failed > > to bind socket > > test_lsm_cgroup_functional:FAIL:start_server unexpected start_server: > > actual -1 < expected 0 > > (network_helpers.c:360: errno: Bad file descriptor) getsockopt(SOL_PROTOCOL) > > test_lsm_cgroup_functional:FAIL:connect_to_fd unexpected > > connect_to_fd: actual -1 < expected 0 > > test_lsm_cgroup_functional:FAIL:accept unexpected accept: actual -1 < expected 0 > > test_lsm_cgroup_functional:FAIL:getsockopt unexpected getsockopt: > > actual -1 < expected 0 > > test_lsm_cgroup_functional:FAIL:sk_priority unexpected sk_priority: > > actual 0 != expected 234 > > ... > > Summary: 0/1 PASSED, 0 SKIPPED, 1 FAILED > > > > > > Song, > > Please follow up with the fix for selftest. > > It will be in bpf-next only. > > We should put that commit on the shared vfs-6.17.bpf branch. The branch had a conflict with bpf-next which was resolved in the merge commit. Then _two_ fixes were applied on top. And one fix is right where conflict was. So it's not possible to apply both fixes to vfs-6.17.bpf. imo this shared branch experience wasn't good. We should have applied the series to bpf-next only. It was more bpf material than vfs. I wouldn't do this again.
On Tue, Jul 01, 2025 at 07:51:55AM -0700, Alexei Starovoitov wrote: > On Tue, Jul 1, 2025 at 1:32 AM Christian Brauner <brauner@kernel.org> wrote: > > > > On Thu, Jun 26, 2025 at 07:14:20PM -0700, Alexei Starovoitov wrote: > > > On Mon, Jun 23, 2025 at 4:03 AM Christian Brauner <brauner@kernel.org> wrote: > > > > > > > > On Sun, 22 Jun 2025 23:38:50 -0700, Song Liu wrote: > > > > > Introduce a new kfunc bpf_cgroup_read_xattr, which can read xattr from > > > > > cgroupfs nodes. The primary users are LSMs, cgroup programs, and sched_ext. > > > > > > > > > > > > > Applied to the vfs-6.17.bpf branch of the vfs/vfs.git tree. > > > > Patches in the vfs-6.17.bpf branch should appear in linux-next soon. > > > > > > Thanks. > > > Now merged into bpf-next/master as well. > > > > > > > Please report any outstanding bugs that were missed during review in a > > > > new review to the original patch series allowing us to drop it. > > > > > > bugs :( > > > > > > > It's encouraged to provide Acked-bys and Reviewed-bys even though the > > > > patch has now been applied. If possible patch trailers will be updated. > > > > > > Pls don't. Keep it as-is, otherwise there will be merge conflicts > > > during the merge window. > > > > This is just the common blurb. As soon as another part of the tree > > relies on something we stabilize the branch and only do fixes on top and > > never rebase. We usually recommend just pulling the branch which I think > > you did. > > > > > > > > > Note that commit hashes shown below are subject to change due to rebase, > > > > trailer updates or similar. If in doubt, please check the listed branch. > > > > > > > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git > > > > branch: vfs-6.17.bpf > > > > > > > > [1/4] kernfs: remove iattr_mutex > > > > https://git.kernel.org/vfs/vfs/c/d1f4e9026007 > > > > [2/4] bpf: Introduce bpf_cgroup_read_xattr to read xattr of cgroup's node > > > > https://git.kernel.org/vfs/vfs/c/535b070f4a80 > > > > [3/4] bpf: Mark cgroup_subsys_state->cgroup RCU safe > > > > https://git.kernel.org/vfs/vfs/c/1504d8c7c702 > > > > [4/4] selftests/bpf: Add tests for bpf_cgroup_read_xattr > > > > https://git.kernel.org/vfs/vfs/c/f4fba2d6d282 > > > > > > Something wrong with this selftest. > > > Cleanup is not done correctly. > > > > > > ./test_progs -t lsm_cgroup > > > Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED > > > ./test_progs -t lsm_cgroup > > > Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED > > > ./test_progs -t cgroup_xattr > > > Summary: 1/8 PASSED, 0 SKIPPED, 0 FAILED > > > ./test_progs -t lsm_cgroup > > > test_lsm_cgroup_functional:PASS:bind(ETH_P_ALL) 0 nsec > > > (network_helpers.c:121: errno: Cannot assign requested address) Failed > > > to bind socket > > > test_lsm_cgroup_functional:FAIL:start_server unexpected start_server: > > > actual -1 < expected 0 > > > (network_helpers.c:360: errno: Bad file descriptor) getsockopt(SOL_PROTOCOL) > > > test_lsm_cgroup_functional:FAIL:connect_to_fd unexpected > > > connect_to_fd: actual -1 < expected 0 > > > test_lsm_cgroup_functional:FAIL:accept unexpected accept: actual -1 < expected 0 > > > test_lsm_cgroup_functional:FAIL:getsockopt unexpected getsockopt: > > > actual -1 < expected 0 > > > test_lsm_cgroup_functional:FAIL:sk_priority unexpected sk_priority: > > > actual 0 != expected 234 > > > ... > > > Summary: 0/1 PASSED, 0 SKIPPED, 1 FAILED > > > > > > > > > Song, > > > Please follow up with the fix for selftest. > > > It will be in bpf-next only. > > > > We should put that commit on the shared vfs-6.17.bpf branch. > > The branch had a conflict with bpf-next which was resolved > in the merge commit. Then _two_ fixes were applied on top. > And one fix is right where conflict was. > So it's not possible to apply both fixes to vfs-6.17.bpf. > imo this shared branch experience wasn't good. > We should have applied the series to bpf-next only. > It was more bpf material than vfs. I wouldn't do this again. Absolutely not. Anything that touches VFS will go through VFS. Shared branches work just fine. We manage to do this with everyone else in the kernel so bpf is able to do this as well. If you'd just asked this would not have been an issue. Merge conflicts are a fact of kernel development, we all deal with it you can too.
On Thu, Jun 26, 2025 at 7:14 PM Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote: [...] > ./test_progs -t lsm_cgroup > Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED > ./test_progs -t lsm_cgroup > Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED > ./test_progs -t cgroup_xattr > Summary: 1/8 PASSED, 0 SKIPPED, 0 FAILED > ./test_progs -t lsm_cgroup > test_lsm_cgroup_functional:PASS:bind(ETH_P_ALL) 0 nsec > (network_helpers.c:121: errno: Cannot assign requested address) Failed > to bind socket > test_lsm_cgroup_functional:FAIL:start_server unexpected start_server: > actual -1 < expected 0 > (network_helpers.c:360: errno: Bad file descriptor) getsockopt(SOL_PROTOCOL) > test_lsm_cgroup_functional:FAIL:connect_to_fd unexpected > connect_to_fd: actual -1 < expected 0 > test_lsm_cgroup_functional:FAIL:accept unexpected accept: actual -1 < expected 0 > test_lsm_cgroup_functional:FAIL:getsockopt unexpected getsockopt: > actual -1 < expected 0 > test_lsm_cgroup_functional:FAIL:sk_priority unexpected sk_priority: > actual 0 != expected 234 > ... > Summary: 0/1 PASSED, 0 SKIPPED, 1 FAILED > > > Song, > Please follow up with the fix for selftest. > It will be in bpf-next only. The issue is because cgroup_xattr calls "ip link set dev lo up" in setup, and calls "ip link set dev lo down" in cleanup. Most other tests only call "ip link set dev lo up". IOW, it appears to me that cgroup_xattr is doing the cleanup properly. To fix this, we can either remove "dev lo down" from cgroup_xattr, or add "dev lo up" to lsm_cgroups. Do you have any preference one way or another? Thanks, Song
On Thu, Jun 26, 2025 at 9:04 PM Song Liu <song@kernel.org> wrote: > > On Thu, Jun 26, 2025 at 7:14 PM Alexei Starovoitov > <alexei.starovoitov@gmail.com> wrote: > [...] > > ./test_progs -t lsm_cgroup > > Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED > > ./test_progs -t lsm_cgroup > > Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED > > ./test_progs -t cgroup_xattr > > Summary: 1/8 PASSED, 0 SKIPPED, 0 FAILED > > ./test_progs -t lsm_cgroup > > test_lsm_cgroup_functional:PASS:bind(ETH_P_ALL) 0 nsec > > (network_helpers.c:121: errno: Cannot assign requested address) Failed > > to bind socket > > test_lsm_cgroup_functional:FAIL:start_server unexpected start_server: > > actual -1 < expected 0 > > (network_helpers.c:360: errno: Bad file descriptor) getsockopt(SOL_PROTOCOL) > > test_lsm_cgroup_functional:FAIL:connect_to_fd unexpected > > connect_to_fd: actual -1 < expected 0 > > test_lsm_cgroup_functional:FAIL:accept unexpected accept: actual -1 < expected 0 > > test_lsm_cgroup_functional:FAIL:getsockopt unexpected getsockopt: > > actual -1 < expected 0 > > test_lsm_cgroup_functional:FAIL:sk_priority unexpected sk_priority: > > actual 0 != expected 234 > > ... > > Summary: 0/1 PASSED, 0 SKIPPED, 1 FAILED > > > > > > Song, > > Please follow up with the fix for selftest. > > It will be in bpf-next only. > > The issue is because cgroup_xattr calls "ip link set dev lo up" > in setup, and calls "ip link set dev lo down" in cleanup. Most > other tests only call "ip link set dev lo up". IOW, it appears to > me that cgroup_xattr is doing the cleanup properly. To fix this, > we can either remove "dev lo down" from cgroup_xattr, or add > "dev lo up" to lsm_cgroups. Do you have any preference one > way or another? It messes with "lo" without switching netns? Ouch. Not sure what tests you copied that code from, but all "ip" commands, ping_group_range, and sockets don't need to be in the test. Instead of triggering progs through lsm/socket_connect hook can't you use a simple hook like lsm/bpf or lsm/file_open that doesn't require networking setup ?
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