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securityfs: fix use-after-free on symlink traversal

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[ Upstream commit 46c874419652bbefdfed17420fd6e88d8a31d9ec ]

symlink body shouldn't be freed without an RCU delay.  Switch securityfs
to ->destroy_inode() and use of call_rcu(); free both the inode and symlink
body in the callback.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Al Viro 2019-04-10 14:03:45 -04:00 committed by Greg Kroah-Hartman
parent 5ac12b4917
commit 0319e32b05
1 changed files with 9 additions and 4 deletions
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13
security/inode.c
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@ -26,17 +26,22 @@
static struct vfsmount *mount;
static int mount_count;
static void securityfs_evict_inode(struct inode *inode)
static void securityfs_i_callback(struct rcu_head *head)
{
truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
struct inode *inode = container_of(head, struct inode, i_rcu);
if (S_ISLNK(inode->i_mode))
kfree(inode->i_link);
free_inode_nonrcu(inode);
}
static void securityfs_destroy_inode(struct inode *inode)
{
call_rcu(&inode->i_rcu, securityfs_i_callback);
}
static const struct super_operations securityfs_super_operations = {
.statfs = simple_statfs,
.evict_inode = securityfs_evict_inode,
.destroy_inode = securityfs_destroy_inode,
};
static int fill_super(struct super_block *sb, void *data, int silent)