blob: 839560673c32a992e3b9a4d10e728af2035a8b31 [file] [log] [blame]
From 24ff6663ccfdaf088dfa7acae489cb11ed4f43c4 Mon Sep 17 00:00:00 2001
From: Josef Bacik <>
Date: Thu, 18 Nov 2010 20:52:55 -0500
Subject: fs: call security_d_instantiate in d_obtain_alias V2
From: Josef Bacik <>
commit 24ff6663ccfdaf088dfa7acae489cb11ed4f43c4 upstream.
While trying to track down some NFS problems with BTRFS, I kept noticing I was
getting -EACCESS for no apparent reason. Eric Paris and printk() helped me
figure out that it was SELinux that was giving me grief, with the following
type=AVC msg=audit(1290013638.413:95): avc: denied { 0x800000 } for pid=1772
comm="nfsd" name="" dev=sda1 ino=256 scontext=system_u:system_r:kernel_t:s0
tcontext=system_u:object_r:unlabeled_t:s0 tclass=file
Turns out this is because in d_obtain_alias if we can't find an alias we create
one and do all the normal instantiation stuff, but we don't do the
Usually we are protected from getting a hashed dentry that hasn't yet run
security_d_instantiate() by the parent's i_mutex, but obviously this isn't an
option there, so in order to deal with the case that a second thread comes in
and finds our new dentry before we get to run security_d_instantiate(), we go
ahead and call it if we find a dentry already. Eric assures me that this is ok
as the code checks to see if the dentry has been initialized already so calling
security_d_instantiate() against the same dentry multiple times is ok. With
this patch I'm no longer getting errant -EACCESS values.
Signed-off-by: Josef Bacik <>
Signed-off-by: Al Viro <>
Cc: Chuck Ebbert <>
Signed-off-by: Greg Kroah-Hartman <>
fs/dcache.c | 3 +++
1 file changed, 3 insertions(+)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1176,9 +1176,12 @@ struct dentry *d_obtain_alias(struct ino
+ security_d_instantiate(tmp, inode);
return tmp;
+ if (res && !IS_ERR(res))
+ security_d_instantiate(res, inode);
return res;