From 13cbbfaa55fa5361db005d7263f85fc339ec547c Mon Sep 17 00:00:00 2001 From: "zhangyi (F)" Date: Wed, 6 Nov 2019 17:43:52 +0800 Subject: [PATCH] fs/dcache: move security_d_instantiate() behind attaching dentry to inode 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] [] ext4_xattr_get+0x8c/0x3e0 [ 31.883195] [] ext4_xattr_security_get+0x24/0x40 [ 31.884086] [] generic_getxattr+0x5b/0x90 [ 31.884907] [] smk_fetch+0xb4/0x150 [ 31.885634] [] smack_d_instantiate+0x1c2/0x550 [ 31.886508] [] security_d_instantiate+0x3a/0x80 [ 31.887389] [] d_instantiate_new+0x36/0x130 [ 31.888223] [] ext4_mkdir+0x4af/0x6a0 [ 31.888928] [] vfs_mkdir+0x100/0x280 [ 31.889536] [] SyS_mkdir+0xb6/0x170 [ 31.890255] [] ? trace_do_page_fault+0x95/0x2b0 [ 31.891134] [] entry_SYSCALL_64_fastpath+0x18/0x73 Cc: # 3.16, 4.4 Signed-off-by: zhangyi (F) Signed-off-by: Greg Kroah-Hartman --- fs/dcache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/dcache.c b/fs/dcache.c index a208222ce..233dcceb6 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1907,7 +1907,6 @@ void d_instantiate_new(struct dentry *entry, struct inode *inode) 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)); @@ -1915,6 +1914,7 @@ void d_instantiate_new(struct dentry *entry, struct inode *inode) 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);