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TTY: hvc, fix TTY refcounting 

A -next commit "TTY: HVC, use tty from tty_port" switched the driver
to use tty_port helper for tty refcounting. But it omitted to remove
manual tty refcounting from open, close and hangup. So now we are
getting random crashes caused by use-after-free:
Unable to handle kernel paging request for data at address 0xc0000003f9d550
Faulting instruction address: 0xc0000000001b7f40
Oops: Kernel access of bad area, sig: 11 [#1]
...
NIP: c0000000001b7f40 LR: c0000000001b7f14 CTR: c0000000000e04f0
...
NIP [c0000000001b7f40] .__kmalloc+0x70/0x230
LR [c0000000001b7f14] .__kmalloc+0x44/0x230
Call Trace:
[c0000003f68bf930] [c0000003f68bf9b0] 0xc0000003f68bf9b0 (unreliable)
[c0000003f68bf9e0] [c0000000001e5424] .alloc_fdmem+0x24/0x70
[c0000003f68bfa60] [c0000000001e54f8] .alloc_fdtable+0x88/0x130
[c0000003f68bfaf0] [c0000000001e5924] .dup_fd+0x384/0x450
[c0000003f68bfbd0] [c00000000009a310] .copy_process+0x880/0x11d0
[c0000003f68bfcd0] [c00000000009aee0] .do_fork+0x70/0x400
[c0000003f68bfdc0] [c0000000000141c4] .sys_clone+0x54/0x70
[c0000003f68bfe30] [c000000000009aa0] .ppc_clone+0x8/0xc

Fix that by complete removal of tty_kref_get/put in open/close/hangup
paths.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-and-tested-by: Michael Neuling <mikey@neuling.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: ppc-dev <linuxppc-dev@lists.ozlabs.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
hifive-unleashed-5.1
Jiri Slaby 2012-04-13 10:31:32 +02:00 committed by Greg Kroah-Hartman
parent 59d59b0600
commit a2f892060f
1 changed files with 0 additions and 5 deletions
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5
drivers/tty/hvc/hvc_console.c
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@ -317,8 +317,6 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
/* Check and then increment for fast path open. */
if (hp->port.count++ > 0) {
spin_unlock_irqrestore(&hp->port.lock, flags);
/* FIXME why taking a reference here? */
tty_kref_get(tty);
hvc_kick();
return 0;
} /* else count == 0 */
@ -338,7 +336,6 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
*/
if (rc) {
tty_port_tty_set(&hp->port, NULL);
tty_kref_put(tty);
tty->driver_data = NULL;
tty_port_put(&hp->port);
printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
@ -393,7 +390,6 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
spin_unlock_irqrestore(&hp->port.lock, flags);
}
tty_kref_put(tty);
tty_port_put(&hp->port);
}
@ -433,7 +429,6 @@ static void hvc_hangup(struct tty_struct *tty)
while(temp_open_count) {
--temp_open_count;
tty_kref_put(tty);
tty_port_put(&hp->port);
}
}