Date: Sun, 23 Aug 2020 21:05:06 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r364539 - head/sys/kern Message-ID: <202008232105.07NL56l5047577@repo.freebsd.org>
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Author: mjg Date: Sun Aug 23 21:05:06 2020 New Revision: 364539 URL: https://svnweb.freebsd.org/changeset/base/364539 Log: vfs: support denying access in vaccess_vexec_smr Modified: head/sys/kern/vfs_subr.c Modified: head/sys/kern/vfs_subr.c ============================================================================== --- head/sys/kern/vfs_subr.c Sun Aug 23 21:04:35 2020 (r364538) +++ head/sys/kern/vfs_subr.c Sun Aug 23 21:05:06 2020 (r364539) @@ -5041,8 +5041,6 @@ vn_isdisk(struct vnode *vp) /* * VOP_FPLOOKUP_VEXEC routines are subject to special circumstances, see * the comment above cache_fplookup for details. - * - * We never deny as priv_check_cred calls are not yet supported, see vaccess. */ int vaccess_vexec_smr(mode_t file_mode, uid_t file_uid, gid_t file_gid, struct ucred *cred) @@ -5054,20 +5052,32 @@ vaccess_vexec_smr(mode_t file_mode, uid_t file_uid, gi if (cred->cr_uid == file_uid) { if (file_mode & S_IXUSR) return (0); - return (EAGAIN); + goto out_error; } /* Otherwise, check the groups (first match) */ if (groupmember(file_gid, cred)) { if (file_mode & S_IXGRP) return (0); - return (EAGAIN); + goto out_error; } /* Otherwise, check everyone else. */ if (file_mode & S_IXOTH) return (0); - return (EAGAIN); +out_error: + /* + * Permission check failed. + * + * vaccess() calls priv_check_cred which in turn can descent into MAC + * modules overriding this result. It's quite unclear what semantics + * are allowed for them to operate, thus for safety we don't call them + * from within the SMR section. This also means if any such modules + * are present, we have to let the regular lookup decide. + */ + if (__predict_false(mac_priv_check_fp_flag || mac_priv_grant_fp_flag)) + return (EAGAIN); + return (EACCES); } /*
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