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From: Al Viro <viro@ZenIV.linux.org.uk>
To: linux-fsdevel@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	linux-kernel@vger.kernel.org, Aleksa Sarai <cyphar@cyphar.com>,
	David Howells <dhowells@redhat.com>,
	Eric Biederman <ebiederm@xmission.com>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Al Viro <viro@zeniv.linux.org.uk>
Subject: [PATCH 3/9] merging pick_link() with get_link(), part 3
Date: Sun, 19 Jan 2020 03:17:32 +0000	[thread overview]
Message-ID: <20200119031738.2681033-20-viro@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20200119031738.2681033-1-viro@ZenIV.linux.org.uk>

From: Al Viro <viro@zeniv.linux.org.uk>

After a pure jump ("/" or procfs-style symlink) we don't need to
hold the link anymore.  link_path_walk() dropped it if such case
had been detected, lookup_last/do_last() (i.e. old trailing_symlink())
left it on the stack - it ended up calling terminate_walk() shortly
anyway, which would've purged the entire stack.

Do it in get_link() itself instead.  Simpler logics that way...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/namei.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index d93e155caded..fe03e4d1144b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1153,7 +1153,9 @@ const char *get_link(struct nameidata *nd)
 		} else {
 			res = get(dentry, inode, &last->done);
 		}
-		if (IS_ERR_OR_NULL(res))
+		if (!res)
+			goto all_done;
+		if (IS_ERR(res))
 			return res;
 	}
 	if (*res == '/') {
@@ -1163,9 +1165,11 @@ const char *get_link(struct nameidata *nd)
 		while (unlikely(*++res == '/'))
 			;
 	}
-	if (!*res)
-		res = NULL;
-	return res;
+	if (*res)
+		return res;
+all_done: // pure jump
+	put_link(nd);
+	return NULL;
 }
 
 /*
@@ -2210,11 +2214,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
 
 			if (IS_ERR(s))
 				return PTR_ERR(s);
-			err = 0;
-			if (unlikely(!s)) {
-				/* jumped */
-				put_link(nd);
-			} else {
+			if (likely(s)) {
 				nd->stack[nd->depth - 1].name = name;
 				name = s;
 				continue;
-- 
2.20.1


  parent reply	other threads:[~2020-01-19  3:24 UTC|newest]

Thread overview: 91+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-30  5:20 [PATCH RFC 0/1] mount: universally disallow mounting over symlinks Aleksa Sarai
2019-12-30  5:20 ` [PATCH RFC 1/1] " Aleksa Sarai
2019-12-30  7:34   ` Linus Torvalds
2019-12-30  8:28     ` Aleksa Sarai
2020-01-08  4:39       ` Andy Lutomirski
2019-12-30  5:44 ` [PATCH RFC 0/1] " Al Viro
2019-12-30  5:49   ` Aleksa Sarai
     [not found]     ` <20191230072959.62kcojxpthhdwmfa@yavin.dot.cyphar.com>
2019-12-30  7:53       ` Linus Torvalds
2019-12-30  8:32         ` Aleksa Sarai
2020-01-02  8:58           ` David Laight
2020-01-02  9:09             ` Aleksa Sarai
2020-01-01  0:43       ` Al Viro
2020-01-01  0:54         ` Al Viro
2020-01-01  3:08           ` Al Viro
2020-01-01 14:44             ` Aleksa Sarai
2020-01-01 23:40               ` Al Viro
2020-01-02  3:59                 ` Aleksa Sarai
2020-01-03  1:49                   ` Al Viro
2020-01-04  4:46                     ` Ian Kent
2020-01-08  3:13                     ` Al Viro
2020-01-08  3:54                       ` Linus Torvalds
2020-01-08 21:34                         ` Al Viro
2020-01-10  0:08                           ` Linus Torvalds
2020-01-10  4:15                             ` Al Viro
2020-01-10  5:03                               ` Linus Torvalds
2020-01-10  6:20                               ` Ian Kent
2020-01-12 21:33                                 ` Al Viro
2020-01-13  2:59                                   ` Ian Kent
2020-01-14  0:25                                     ` Ian Kent
2020-01-14  4:39                                       ` Al Viro
2020-01-14  5:01                                         ` Ian Kent
2020-01-14  5:59                                           ` Ian Kent
2020-01-10 21:07                         ` Aleksa Sarai
2020-01-14  4:57                           ` Al Viro
2020-01-14  5:12                             ` Al Viro
2020-01-14 20:01                             ` Aleksa Sarai
2020-01-15 14:25                               ` Al Viro
2020-01-15 14:29                                 ` Aleksa Sarai
2020-01-15 14:34                                   ` Aleksa Sarai
2020-01-15 14:48                                     ` Al Viro
2020-01-18 12:07                                       ` [PATCH v3 0/2] openat2: minor uapi cleanups Aleksa Sarai
2020-01-18 12:07                                         ` [PATCH v3 1/2] open: introduce openat2(2) syscall Aleksa Sarai
2020-01-18 12:08                                         ` [PATCH v3 2/2] selftests: add openat2(2) selftests Aleksa Sarai
2020-01-18 15:28                                         ` [PATCH v3 0/2] openat2: minor uapi cleanups Al Viro
2020-01-18 18:09                                           ` Al Viro
2020-01-18 23:03                                             ` Aleksa Sarai
2020-01-19  1:12                                               ` Al Viro
2020-01-15 13:57                             ` [PATCH RFC 0/1] mount: universally disallow mounting over symlinks Aleksa Sarai
2020-01-19  3:14                               ` [RFC][PATCHSET][CFT] pathwalk cleanups and fixes Al Viro
2020-01-19  3:17                                 ` [PATCH 01/17] do_add_mount(): lift lock_mount/unlock_mount into callers Al Viro
2020-01-19  3:17                                   ` [PATCH 02/17] fix automount/automount race properly Al Viro
2020-01-30 14:34                                     ` Christian Brauner
2020-01-19  3:17                                   ` [PATCH 03/17] follow_automount(): get rid of dead^Wstillborn code Al Viro
2020-01-30 14:38                                     ` Christian Brauner
2020-01-19  3:17                                   ` [PATCH 04/17] follow_automount() doesn't need the entire nameidata Al Viro
2020-01-30 14:45                                     ` Christian Brauner
2020-01-30 15:38                                       ` Al Viro
2020-01-30 15:55                                         ` Al Viro
2020-01-19  3:17                                   ` [PATCH 05/17] make build_open_flags() treat O_CREAT | O_EXCL as implying O_NOFOLLOW Al Viro
2020-01-19  3:17                                   ` [PATCH 06/17] handle_mounts(): start building a sane wrapper for follow_managed() Al Viro
2020-01-19  3:17                                   ` [PATCH 07/17] atomic_open(): saner calling conventions (return dentry on success) Al Viro
2020-01-19  3:17                                   ` [PATCH 08/17] lookup_open(): " Al Viro
2020-01-19  3:17                                   ` [PATCH 09/17] do_last(): collapse the call of path_to_nameidata() Al Viro
2020-01-19  3:17                                   ` [PATCH 10/17] handle_mounts(): pass dentry in, turn path into a pure out argument Al Viro
2020-01-19  3:17                                   ` [PATCH 11/17] lookup_fast(): consolidate the RCU success case Al Viro
2020-01-19  3:17                                   ` [PATCH 12/17] teach handle_mounts() to handle RCU mode Al Viro
2020-01-19  3:17                                   ` [PATCH 13/17] lookup_fast(): take mount traversal into callers Al Viro
2020-01-19  3:17                                   ` [PATCH 14/17] new step_into() flag: WALK_NOFOLLOW Al Viro
2020-01-19  3:17                                   ` [PATCH 15/17] fold handle_mounts() into step_into() Al Viro
2020-01-19  3:17                                   ` [PATCH 16/17] LOOKUP_MOUNTPOINT: fold path_mountpointat() into path_lookupat() Al Viro
2020-01-19  3:17                                   ` [PATCH 17/17] expand the only remaining call of path_lookup_conditional() Al Viro
2020-01-19  3:17                                   ` [PATCH 1/9] merging pick_link() with get_link(), part 1 Al Viro
2020-01-19  3:17                                   ` [PATCH 2/9] merging pick_link() with get_link(), part 2 Al Viro
2020-01-19  3:17                                   ` Al Viro [this message]
2020-01-19  3:17                                   ` [PATCH 4/9] merging pick_link() with get_link(), part 4 Al Viro
2020-01-19  3:17                                   ` [PATCH 5/9] merging pick_link() with get_link(), part 5 Al Viro
2020-01-19  3:17                                   ` [PATCH 6/9] merging pick_link() with get_link(), part 6 Al Viro
2020-01-19  3:17                                   ` [PATCH 7/9] finally fold get_link() into pick_link() Al Viro
2020-01-19  3:17                                   ` [PATCH 8/9] massage __follow_mount_rcu() a bit Al Viro
2020-01-19  3:17                                   ` [PATCH 9/9] new helper: traverse_mounts() Al Viro
2020-01-30 14:13                                   ` [PATCH 01/17] do_add_mount(): lift lock_mount/unlock_mount into callers Christian Brauner
2020-01-19 14:33                                 ` [RFC][PATCHSET][CFT] pathwalk cleanups and fixes Ian Kent
2020-01-10 23:19                     ` [PATCH RFC 0/1] mount: universally disallow mounting over symlinks Al Viro
2020-01-13  1:48                       ` Ian Kent
2020-01-13  3:54                         ` Al Viro
2020-01-13  6:00                           ` Ian Kent
2020-01-13  6:03                             ` Ian Kent
2020-01-13 13:30                               ` Al Viro
2020-01-14  7:25                                 ` Ian Kent
2020-01-14 12:17                                   ` Ian Kent
2020-01-04  5:52               ` Andy Lutomirski

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