| From 24ff6663ccfdaf088dfa7acae489cb11ed4f43c4 Mon Sep 17 00:00:00 2001 |
| From: Josef Bacik <josef@redhat.com> |
| Date: Thu, 18 Nov 2010 20:52:55 -0500 |
| Subject: fs: call security_d_instantiate in d_obtain_alias V2 |
| |
| 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> |
| Cc: Chuck Ebbert <cebbert@redhat.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
| |
| --- |
| 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 |
| 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; |
| } |
