aboutsummaryrefslogtreecommitdiffstats
path: root/fs/proc/proc_sysctl.c
diff options
context:
space:
mode:
authorLucas De Marchi <lucas.demarchi@profusion.mobi>2012-03-22 14:42:22 -0700
committerEric W. Biederman <ebiederm@xmission.com>2012-03-22 14:46:56 -0700
commit4e474a00d7ff746ed177ddae14fa8b2d4bad7a00 (patch)
tree1255e88406191e4daa29e59ebd37fdc8042184e4 /fs/proc/proc_sysctl.c
parent4e75732035d7e97e001bdf6e3149d3967c0221de (diff)
sysctl: protect poll() in entries that may go away
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> Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Diffstat (limited to 'fs/proc/proc_sysctl.c')
-rw-r--r--fs/proc/proc_sysctl.c17
1 files changed, 16 insertions, 1 deletions
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index a7708b7c957..47b474b572c 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -525,20 +525,32 @@ 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;
@@ -546,6 +558,7 @@ 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)) {
@@ -554,6 +567,8 @@ static unsigned int proc_sys_poll(struct file *filp, poll_table *wait)
}
out:
+ sysctl_head_finish(head);
+
return ret;
}