diff options
| author | Lucas De Marchi <lucas.demarchi@profusion.mobi> | 2012-03-22 14:42:22 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-04-02 09:52:52 -0700 |
| commit | eebfd5e734d12b915ebff75690e63e80678f3609 (patch) | |
| tree | 0165d15ea56ab124013b1fe2425394f2e5344050 /fs | |
| parent | ab153f21e011985dbe056f8780c31d823db8948e (diff) | |
sysctl: protect poll() in entries that may go away
commit 4e474a00d7ff746ed177ddae14fa8b2d4bad7a00 upstream.
Protect code accessing ctl_table by grabbing the header with grab_header()
and after releasing with sysctl_head_finish(). This is needed if poll()
is called in entries created by modules: currently only hostname and
domainname support poll(), but this bug may be triggered when/if modules
use it and if user called poll() in a file that doesn't support it.
Dave Jones reported the following when using a syscall fuzzer while
hibernating/resuming:
RIP: 0010:[<ffffffff81233e3e>] [<ffffffff81233e3e>] proc_sys_poll+0x4e/0x90
RAX: 0000000000000145 RBX: ffff88020cab6940 RCX: 0000000000000000
RDX: ffffffff81233df0 RSI: 6b6b6b6b6b6b6b6b RDI: ffff88020cab6940
[ ... ]
Code: 00 48 89 fb 48 89 f1 48 8b 40 30 4c 8b 60 e8 b8 45 01 00 00 49 83
7c 24 28 00 74 2e 49 8b 74 24 30 48 85 f6 74 24 48 85 c9 75 32 <8b> 16
b8 45 01 00 00 48 63 d2 49 39 d5 74 10 8b 06 48 98 48 89
If an entry goes away while we are polling() it, ctl_table may not exist
anymore.
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/proc/proc_sysctl.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index a6b62173d4c..53c3bcea56c 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -188,20 +188,32 @@ static ssize_t proc_sys_write(struct file *filp, const char __user *buf, static int proc_sys_open(struct inode *inode, struct file *filp) { + struct ctl_table_header *head = grab_header(inode); struct ctl_table *table = PROC_I(inode)->sysctl_entry; + /* sysctl was unregistered */ + if (IS_ERR(head)) + return PTR_ERR(head); + if (table->poll) filp->private_data = proc_sys_poll_event(table->poll); + sysctl_head_finish(head); + return 0; } static unsigned int proc_sys_poll(struct file *filp, poll_table *wait) { struct inode *inode = filp->f_path.dentry->d_inode; + struct ctl_table_header *head = grab_header(inode); struct ctl_table *table = PROC_I(inode)->sysctl_entry; - unsigned long event = (unsigned long)filp->private_data; unsigned int ret = DEFAULT_POLLMASK; + unsigned long event; + + /* sysctl was unregistered */ + if (IS_ERR(head)) + return POLLERR | POLLHUP; if (!table->proc_handler) goto out; @@ -209,6 +221,7 @@ static unsigned int proc_sys_poll(struct file *filp, poll_table *wait) if (!table->poll) goto out; + event = (unsigned long)filp->private_data; poll_wait(filp, &table->poll->wait, wait); if (event != atomic_read(&table->poll->event)) { @@ -217,6 +230,8 @@ static unsigned int proc_sys_poll(struct file *filp, poll_table *wait) } out: + sysctl_head_finish(head); + return ret; } |