| From | Andi Kleen <> | Subject | [PATCH] [241/275] fs: call security_d_instantiate in d_obtain_alias V2 | Date | Wed, 30 Mar 2011 14:08:07 -0700 (PDT) |
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2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------ From: Josef Bacik <josef@redhat.com>
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 denial
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 security_d_instantiate.
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 <josef@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andi Kleen <ak@linux.intel.com> Cc: Chuck Ebbert <cebbert@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- fs/dcache.c | 3 +++ 1 file changed, 3 insertions(+)
Index: linux-2.6.35.y/fs/dcache.c =================================================================== --- linux-2.6.35.y.orig/fs/dcache.c 2011-03-29 22:50:16.864826890 -0700 +++ linux-2.6.35.y/fs/dcache.c 2011-03-29 23:03:03.231217492 -0700 @@ -1186,9 +1186,12 @@ spin_unlock(&tmp->d_lock); spin_unlock(&dcache_lock); + security_d_instantiate(tmp, inode); return tmp; out_iput: + if (res && !IS_ERR(res)) + security_d_instantiate(res, inode); iput(inode); return res; }
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