From: "zhangyi (F)" yi.zhang@huawei.com
During backport 1e2e547a93a "do d_instantiate/unlock_new_inode combinations safely", there was a error instantiating sequence of attaching dentry to inode and calling security_d_instantiate().
Before commit ce23e640133 "->getxattr(): pass dentry and inode as separate arguments" and b96809173e9 "security_d_instantiate(): move to the point prior to attaching dentry to inode", security_d_instantiate() should be called beind __d_instantiate(), otherwise it will trigger below problem when CONFIG_SECURITY_SMACK on ext4 was enabled because d_inode(dentry) used by ->getxattr() is NULL before __d_instantiate() instantiate inode.
[ 31.858026] BUG: unable to handle kernel paging request at ffffffffffffff70 ... [ 31.882024] Call Trace: [ 31.882378] [<ffffffffa347f75c>] ext4_xattr_get+0x8c/0x3e0 [ 31.883195] [<ffffffffa3489454>] ext4_xattr_security_get+0x24/0x40 [ 31.884086] [<ffffffffa336a56b>] generic_getxattr+0x5b/0x90 [ 31.884907] [<ffffffffa3700514>] smk_fetch+0xb4/0x150 [ 31.885634] [<ffffffffa3700772>] smack_d_instantiate+0x1c2/0x550 [ 31.886508] [<ffffffffa36f9a5a>] security_d_instantiate+0x3a/0x80 [ 31.887389] [<ffffffffa3353b26>] d_instantiate_new+0x36/0x130 [ 31.888223] [<ffffffffa342b1ef>] ext4_mkdir+0x4af/0x6a0 [ 31.888928] [<ffffffffa3343470>] vfs_mkdir+0x100/0x280 [ 31.889536] [<ffffffffa334b086>] SyS_mkdir+0xb6/0x170 [ 31.890255] [<ffffffffa307c855>] ? trace_do_page_fault+0x95/0x2b0 [ 31.891134] [<ffffffffa3c5e078>] entry_SYSCALL_64_fastpath+0x18/0x73
Cc: stable@vger.kernel.org # 3.16, 4.4 Signed-off-by: zhangyi (F) yi.zhang@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/dcache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/dcache.c +++ b/fs/dcache.c @@ -1903,7 +1903,6 @@ void d_instantiate_new(struct dentry *en BUG_ON(!hlist_unhashed(&entry->d_u.d_alias)); BUG_ON(!inode); lockdep_annotate_inode_mutex_key(inode); - security_d_instantiate(entry, inode); spin_lock(&inode->i_lock); __d_instantiate(entry, inode); WARN_ON(!(inode->i_state & I_NEW)); @@ -1911,6 +1910,7 @@ void d_instantiate_new(struct dentry *en smp_mb(); wake_up_bit(&inode->i_state, __I_NEW); spin_unlock(&inode->i_lock); + security_d_instantiate(entry, inode); } EXPORT_SYMBOL(d_instantiate_new);