Enable writing xattr from BPF programs #4774
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Introduct new xattr name prefix security.bpf., and enable reading these xattrs from bpf kfuncs bpf_get_[file|dentry]_xattr(). As we are on it, correct the comments for return value of bpf_get_[file|dentry]_xattr(), i.e. return length the xattr value on success. Signed-off-by: Song Liu <[email protected]> Acked-by: Christian Brauner <[email protected]>
Extend test_progs fs_kfuncs to cover different xattr names. Specifically: xattr name "user.kfuncs" and "security.bpf.xxx" can be read from BPF program with kfuncs bpf_get_[file|dentry]_xattr(); while "security.bpf" and "security.selinux" cannot be read. Signed-off-by: Song Liu <[email protected]>
Add bpf_lsm_inode_removexattr and bpf_lsm_inode_post_removexattr to list sleepable_lsm_hooks. These two hooks are always called from sleepable context. Signed-off-by: Song Liu <[email protected]>
Add the following kfuncs to set and remove xattrs from BPF programs: bpf_set_dentry_xattr bpf_remove_dentry_xattr bpf_set_dentry_xattr_locked bpf_remove_dentry_xattr_locked The _locked version of these kfuncs are called from hooks where dentry->d_inode is already locked. Signed-off-by: Song Liu <[email protected]>
Two sets of tests are added to exercise the not _locked and _locked version of the kfuncs. For both tests, user space accesses xattr security.bpf.foo on a testfile. The BPF program is triggered by user space access (on LSM hook inode_[set|get]_xattr) and sets or removes xattr security.bpf.bar. Then user space then validates that xattr security.bpf.bar is set or removed as expected. Signed-off-by: Song Liu <[email protected]>
Different LSM hooks should call different versions of set/remove xattr kfuncs (with _locked or not). Add __failure tests to make sure the verifier can detect when the user uses the wrong kfuncs. Signed-off-by: Song Liu <[email protected]>
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Upstream branch: 6e8ba49 |
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Pull request for series with
subject: Enable writing xattr from BPF programs
version: 3
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=916534