git: f9b923af34a6 - main - O_PATH: Allow to open symlink

[Konstantin Belousov]

The branch main has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=f9b923af34a6749c7703b957742f33cc02a485a2

commit f9b923af34a6749c7703b957742f33cc02a485a2
Author:     Konstantin Belousov <kib at FreeBSD.org>
AuthorDate: 2021-04-07 03:23:25 +0000
Commit:     Konstantin Belousov <kib at FreeBSD.org>
CommitDate: 2021-04-15 09:49:09 +0000

    O_PATH: Allow to open symlink
    
    When O_NOFOLLOW is specified, namei() returns the symlink itself.  In
    this case, open(O_PATH) should be allowed, to denote the location of symlink
    itself.
    
    Prevent O_EXEC in this case, execve(2) code is not ready to try to execute
    symlinks.
    
    Reported by:    wulf
    Reviewed by:    markj
    Tested by:      pho
    Sponsored by:   The FreeBSD Foundation
    MFC after:      1 week
    Differential revision:  https://reviews.freebsd.org/D29323
---
 sys/kern/vfs_vnops.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index 6339295b0556..bb9ee2cceb79 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -385,8 +385,10 @@ vn_open_vnode(struct vnode *vp, int fmode, struct ucred *cred,
 	accmode_t accmode;
 	int error;
 
-	if (vp->v_type == VLNK)
-		return (EMLINK);
+	if (vp->v_type == VLNK) {
+		if ((fmode & O_PATH) == 0 || (fmode & FEXEC) != 0)
+			return (EMLINK);
+	}
 	if (vp->v_type == VSOCK)
 		return (EOPNOTSUPP);
 	if (vp->v_type != VDIR && fmode & O_DIRECTORY)