SELinux: properly handle empty tty_files list
PATCH 1/1 SELinux: properly handle empty tty_files list
SELinux: handle empty tty_files list
From: Eric Paris <[email protected]>
SELinux has wrongly (since 2004) had an incorrect test for an empty tty->tty_files list. With an empty list selinux would be pointing to part of the tty struct itself and would then proceed to dereference that value and again dereference that result. An F10 change to plymouth on a ppc64 system is actually currently triggering this bug. This patch uses list_empty() to handle empty lists rather than looking at a meaningless location.
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security/selinux/hooks.c | 8 +++++--- 1 files changed, 5 insertions(+), 3 deletions(-)
security/selinux/hooks.c +5 -3
@@ -2126,14 +2126,16 @@ static inline void flush_unauthorized_files(struct files_struct *files) tty =get_current_tty ();if (tty) {file_list_lock (); - file =list_entry (tty->tty_files.next,typeof (*file), f_u.fu_list); -if (file) { +if (!list_empty (&tty->tty_files)) { +struct inode *inode; +/* Revalidate access to controlling tty. Use inode_has_perm on the tty inode directly rather than using file_has_perm, as this particular open file may belong to another process and we are only interested in the inode-based check here. */ -struct inode *inode = file->f_path.dentry->d_inode; + file = list_first_entry(&tty->tty_files, struct file, f_u.fu_list); + inode = file->f_path.dentry->d_inode;if (inode_has_perm (current, inode,FILE__READ |FILE__WRITE ,NULL )) { drop_tty =1 ;
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