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authorNick Piggin <npiggin@kernel.dk>2010-08-18 04:37:36 +1000
committerAl Viro <viro@zeniv.linux.org.uk>2010-08-18 08:35:47 -0400
commitd996b62a8df1d935b01319bf8defb95b5709f7b8 (patch)
treed81f8240da776336845a2063555d7bb4dce684bd /security
parentee2ffa0dfdd2db19705f2ba1c6a4c0bfe8122dd8 (diff)
downloadlinux-2.6.38-lt-ux500-d996b62a8df1d935b01319bf8defb95b5709f7b8.tar.gz
tty: fix fu_list abuse
tty: fix fu_list abuse tty code abuses fu_list, which causes a bug in remount,ro handling. If a tty device node is opened on a filesystem, then the last link to the inode removed, the filesystem will be allowed to be remounted readonly. This is because fs_may_remount_ro does not find the 0 link tty inode on the file sb list (because the tty code incorrectly removed it to use for its own purpose). This can result in a filesystem with errors after it is marked "clean". Taking idea from Christoph's initial patch, allocate a tty private struct at file->private_data and put our required list fields in there, linking file and tty. This makes tty nodes behave the same way as other device nodes and avoid meddling with the vfs, and avoids this bug. The error handling is not trivial in the tty code, so for this bugfix, I take the simple approach of using __GFP_NOFAIL and don't worry about memory errors. This is not a problem because our allocator doesn't fail small allocs as a rule anyway. So proper error handling is left as an exercise for tty hackers. [ Arguably filesystem's device inode would ideally be divorced from the driver's pseudo inode when it is opened, but in practice it's not clear whether that will ever be worth implementing. ] Cc: linux-kernel@vger.kernel.org Cc: Christoph Hellwig <hch@infradead.org> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: Nick Piggin <npiggin@kernel.dk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'security')
-rw-r--r--security/selinux/hooks.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index bd7da0f0ccf..4796ddd4e72 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2172,6 +2172,7 @@ static inline void flush_unauthorized_files(const struct cred *cred,
if (tty) {
spin_lock(&tty_files_lock);
if (!list_empty(&tty->tty_files)) {
+ struct tty_file_private *file_priv;
struct inode *inode;
/* Revalidate access to controlling tty.
@@ -2179,7 +2180,9 @@ static inline void flush_unauthorized_files(const struct cred *cred,
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. */
- file = list_first_entry(&tty->tty_files, struct file, f_u.fu_list);
+ file_priv = list_first_entry(&tty->tty_files,
+ struct tty_file_private, list);
+ file = file_priv->file;
inode = file->f_path.dentry->d_inode;
if (inode_has_perm(cred, inode,
FILE__READ | FILE__WRITE, NULL)) {