Messages in this thread Patch in this message | | | Subject | Re: tty: tty_struct memory leak | From | Peter Hurley <> | Date | Wed, 3 Feb 2016 15:27:07 -0800 |
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Hi Dmitry,
On 02/03/2016 08:26 AM, Dmitry Vyukov wrote: > On Wed, Feb 3, 2016 at 5:10 PM, Dmitry Vyukov <dvyukov@google.com> wrote: >> Hello, >> >> The following program causes tty_struct memory leak: >> >> // autogenerated by syzkaller (http://github.com/google/syzkaller) >> #include <pthread.h> >> #include <stdint.h> >> #include <string.h> >> #include <sys/syscall.h> >> #include <unistd.h> >> >> int main() >> { >> alarm(1); >> syscall(SYS_open, "/dev/ircomm7", 0x12d401ul, 0, 0, 0); >> return 0; >> }
Going to need more information than this because the reproducer above does not generate a tty_struct memory leak.
Here's what I did:
Enabled tty debugging and added patch below [1] to show kfree(tty), then:
$ sudo modprobe ircomm $ ./reproducer
Here's what I got:
[ 1436.864342] tty_ldisc_open: ircomm ircomm7: ffff8802aa3b3410: opened [ 1436.864352] tty_open: ircomm ircomm7: opening (count=1) [ 1437.863994] tty_open: ircomm ircomm7: open error -512, releasing [ 1437.864051] tty_release: ircomm ircomm7: releasing (count=1) [ 1437.864055] tty_wait_until_sent: ircomm ircomm7: wait until sent, timeout=7500 [ 1437.864110] tty_release: ircomm ircomm7: final close [ 1437.864120] tty_ldisc_close: ircomm ircomm7: ffff8802aa3b3410: closed [ 1437.864124] tty_ldisc_release: ircomm ircomm7: released [ 1437.864130] tty_release: ircomm ircomm7: release [ 1437.864148] release_one_tty: ircomm ircomm7: freeing structure ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Note that release_one_tty() ends in kfree(tty)
Regards, Peter Hurley
>> unreferenced object 0xffff88002d3c5898 (size 2048): >> comm "a.out", pid 5831, jiffies 4303981829 (age 9.451s) >> hex dump (first 32 bytes): >> 01 54 00 00 1c 00 00 00 98 58 14 63 00 88 ff ff .T.......X.c.... >> 18 ec 12 63 00 88 ff ff c0 45 34 87 ff ff ff ff ...c.....E4..... >> backtrace: >> [< inline >] kzalloc include/linux/slab.h:607 >> [<ffffffff82f871c8>] alloc_tty_struct+0x98/0x820 drivers/tty/tty_io.c:3133 >> [<ffffffff82f879c8>] tty_init_dev+0x78/0x4b0 drivers/tty/tty_io.c:1523 >> [<ffffffff82f88abd>] tty_open+0xcbd/0x1070 drivers/tty/tty_io.c:2082 >> [<ffffffff817c864a>] chrdev_open+0x22a/0x4c0 fs/char_dev.c:388 >> [<ffffffff817b3e72>] do_dentry_open+0x6a2/0xcb0 fs/open.c:736 >> [<ffffffff817b754b>] vfs_open+0x17b/0x1f0 fs/open.c:853 >> [< inline >] do_last fs/namei.c:3254 >> [<ffffffff817ead19>] path_openat+0xde9/0x5e30 fs/namei.c:3386 >> [<ffffffff817f359e>] do_filp_open+0x18e/0x250 fs/namei.c:3421 >> [<ffffffff817b7ccc>] do_sys_open+0x1fc/0x420 fs/open.c:1022 >> [< inline >] SYSC_open fs/open.c:1040 >> [<ffffffff817b7f1d>] SyS_open+0x2d/0x40 fs/open.c:1035 >> [<ffffffff8665ebb6>] entry_SYSCALL_64_fastpath+0x16/0x7a >> arch/x86/entry/entry_64.S:185 >> >> >> # ls -l /dev/ircomm7 >> crw-rw---T 1 root dialout 161, 7 Feb 3 16:03 /dev/ircomm7 >> >> >> On commit 34229b277480f46c1e9a19f027f30b074512e68b > > +syzkaller mailing list >
[1] --- >% --- Subject: [PATCH] debug: log tty freed
--- drivers/tty/tty_io.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 3f4f47a..15f2d6d 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1633,6 +1633,8 @@ static void release_one_tty(struct work_struct *work) struct tty_driver *driver = tty->driver; struct module *owner = driver->owner; + tty_debug_hangup(tty, "freeing structure\n"); + if (tty->ops->cleanup) tty->ops->cleanup(tty); @@ -1909,7 +1911,7 @@ int tty_release(struct inode *inode, struct file *filp) /* Wait for pending work before tty destruction commmences */ tty_flush_works(tty); - tty_debug_hangup(tty, "freeing structure\n"); + tty_debug_hangup(tty, "release\n"); /* * The release_tty function takes care of the details of clearing * the slots and preserving the termios structure. The tty_unlock_pair -- 2.7.0
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