lkml.org 
[lkml]   [2012]   [Dec]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] vfs: remove unneeded permission check from path_init
Date
When path_init is called with a valid dfd, that code checks permissions
on the open directory fd and returns an error if the check fails. This
permission check is redundant, however.

Both callers of path_init immediately call link_path_walk afterward. The
first thing that link_path_walk does is to check for exec permissions
at the starting point of the path walk.

In most cases, these checks are very quick, but when the dfd is for a
file on a NFS mount with the actimeo=0, each permission check goes
out onto the wire. The result is 2 identical ACCESS calls.

Given that these codepaths are fairly "hot", I think it makes sense to
eliminate the permission check in path_init and simply assume that the
caller will eventually check the permissions before proceeding.

Reported-by: Dave Wysochanski <dwysocha@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
fs/namei.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 40d864a..deefbc3 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1894,6 +1894,7 @@ static int path_init(int dfd, const char *name, unsigned int flags,
get_fs_pwd(current->fs, &nd->path);
}
} else {
+ /* Caller must check execute permissions on the starting path component */
struct fd f = fdget_raw(dfd);
struct dentry *dentry;

@@ -1907,12 +1908,6 @@ static int path_init(int dfd, const char *name, unsigned int flags,
fdput(f);
return -ENOTDIR;
}
-
- retval = inode_permission(dentry->d_inode, MAY_EXEC);
- if (retval) {
- fdput(f);
- return retval;
- }
}

nd->path = f.file->f_path;
--
1.7.11.7


\
 
 \ /
  Last update: 2012-12-11 15:01    [W:0.039 / U:0.104 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site