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Wed, 23 Sep 2026 19:20:55 -0700 (PDT) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Thu, 24 Sep 2026 02:20:54 +0000 Message-Id: Cc: , , , Subject: Re: [PATCH bpf] bpf: fs/xattr: don't assume the inode is locked in path_unlink/path_rmdir From: "Alexei Starovoitov" To: "Andrea Parri" , "Alexander Viro" , "Christian Brauner" , "Jan Kara" , "Alexei Starovoitov" , "Matt Bobrowski" , "Song Liu" X-Mailer: aerc 0.20.1-349-gb940a4174a3e-dirty References: <20260922145530.369775-1-parri.andrea@gmail.com> In-Reply-To: <20260922145530.369775-1-parri.andrea@gmail.com> On Tue Sep 22, 2026 at 2:55 PM UTC, Andrea Parri wrote: > bpf_lsm_has_d_inode_locked() makes the verifier rewrite > bpf_[set|remove]_dentry_xattr() to the _locked variants, which assume > that the caller already holds the inode's i_rwsem. The path_unlink and > path_rmdir hooks are listed, but security_path_unlink() and > security_path_rmdir() run before vfs_unlink()/vfs_rmdir() take the > victim inode's i_rwsem, so a sleepable BPF LSM program attached to > either hook mutates the victim's xattrs without the lock held. > > Drop the two path hooks from d_inode_locked_hooks so that the verifier > keeps the locking bpf_[set|remove]_dentry_xattr() variants, which take > the lock themselves. > > Fixes: 56467292794b8 ("bpf: fs/xattr: Add BPF kfuncs to set and remove xa= ttrs") > Cc: stable@vger.kernel.org > Assisted-by: LLM > Signed-off-by: Andrea Parri > --- > fs/bpf_fs_kfuncs.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/fs/bpf_fs_kfuncs.c b/fs/bpf_fs_kfuncs.c > index 6cb8772679782..357a379ef92a5 100644 > --- a/fs/bpf_fs_kfuncs.c > +++ b/fs/bpf_fs_kfuncs.c > @@ -472,10 +472,6 @@ BTF_ID(func, bpf_lsm_inode_rmdir) > BTF_ID(func, bpf_lsm_inode_setattr) > BTF_ID(func, bpf_lsm_inode_setxattr) > BTF_ID(func, bpf_lsm_inode_unlink) > -#ifdef CONFIG_SECURITY_PATH > -BTF_ID(func, bpf_lsm_path_unlink) > -BTF_ID(func, bpf_lsm_path_rmdir) > -#endif /* CONFIG_SECURITY_PATH */ > BTF_SET_END(d_inode_locked_hooks) Christian, this looks correct. Want to take it via vfs?