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authorIan Kent <raven@themaw.net>2008-07-23 21:30:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-24 10:47:32 -0700
commitc72305b5472522299bb6f45b736080128eb1c822 (patch)
tree0dc2c0c553d302358df0b54676ef4be82d47fb6c
parentautofs4: detect invalid direct mount requests (diff)
downloadlinux-dev-c72305b5472522299bb6f45b736080128eb1c822.tar.xz
linux-dev-c72305b5472522299bb6f45b736080128eb1c822.zip
autofs4: indirect dentry must almost always be positive
We have been seeing mount requests comming to the automount daemon for keys of the form "<map key>/<non key directory>" which are lookups for invalid map keys. But we can check for this in the kernel module and return a fail immediately, without having to send a request to the daemon. It is possible to recognise these requests are invalid based on whether the request dentry is negative and its relation to the autofs file system root. For example, given the indirect multi-mount map entry: idm1 \ /mm1 <server>:/<path1> /mm2 <server>:/<path2> For a request to mount idm1, IS_ROOT((idm1)->d_parent) will be always be true and the dentry may be negative. But directories idm1/mm1 and idm1/mm2 will always be created as part of the mount request for idm1. So any mount request within idm1 itself must have a positive dentry otherwise the map key is invalid. In version 4 these multi-mount entries are all mounted and umounted as a single request and in version 5 the directories idm1/mm1 and idm1/mm2 are created and an autofs fs mounted on them to act as a mount trigger so the above is also true. This also holds true for the autofs version 4 pseudo direct mount feature. When this feature is used without the "--ghost" option automount(8) will create internal submounts as we go down the map key paths which are essentially normal indirect mounts for which the above holds. If the "--ghost" option is given the directories for map keys are created at daemon startup so valid map entries correspond to postive dentries in the autofs fs. autofs version 5 direct mount maps are similar except that the IS_ROOT check is not needed. This has been addressed in a previous patch tittled "autofs4 - detect invalid direct mount requests". For example, given the direct multi-mount map entry: /test/dm1 \ /mm1 <server>:/<path1> /mm2 <server>:/<path2> An autofs fs is mounted on /test/dm1 as a trigger mount and when a mount is triggered for /test/dm1, the multi-mount offset directories /test/dm1/mm1 and /test/dm1/mm2 are created and an autofs fs is mounted on them to act as mount triggers. So valid direct mount requests must always have a positive dentry if they correspond to a valid map entry. Signed-off-by: Ian Kent <raven@themaw.net> Acked-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/autofs4/waitq.c17
1 files changed, 14 insertions, 3 deletions
diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
index bcb6c5265467..35216d18d8b5 100644
--- a/fs/autofs4/waitq.c
+++ b/fs/autofs4/waitq.c
@@ -328,9 +328,20 @@ int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
if (sbi->catatonic)
return -ENOENT;
- if (!dentry->d_inode &&
- (sbi->type & (AUTOFS_TYPE_DIRECT | AUTOFS_TYPE_OFFSET)))
- return -ENOENT;
+ if (!dentry->d_inode) {
+ /*
+ * A wait for a negative dentry is invalid for certain
+ * cases. A direct or offset mount "always" has its mount
+ * point directory created and so the request dentry must
+ * be positive or the map key doesn't exist. The situation
+ * is very similar for indirect mounts except only dentrys
+ * in the root of the autofs file system may be negative.
+ */
+ if (sbi->type & (AUTOFS_TYPE_DIRECT|AUTOFS_TYPE_OFFSET))
+ return -ENOENT;
+ else if (!IS_ROOT(dentry->d_parent))
+ return -ENOENT;
+ }
name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
if (!name)