On 07. 04. 21, 4:16, Hillf Danton wrote:
Add the error path for registering tty devices and roll back in case of error
in bid to avoid the UAF like the below one reported.
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 8923 at lib/refcount.c:28
refcount_warn_saturate+0x1cf/0x210 -origin/lib/refcount.c:28
Modules linked in:
CPU: 1 PID: 8923 Comm: executor Not tainted 5.12.0-rc5+ #8
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:refcount_warn_saturate+0x1cf/0x210 -origin/lib/refcount.c:28
Code: 4f ff ff ff e8 32 fa b5 fe 48 c7 c7 3d f8 f6 86 e8 d6 ab c6 fe
c6 05 7c 34 67 04 01 48 c7 c7 68 f8 6d 86 31 c0 e8 81 2e 9d fe <0f> 0b
e9 22 ff ff ff e8 05 fa b5 fe 48 c7 c7 3e f8 f6 86 e8 a9 ab
RSP: 0018:ffffc90001633c60 EFLAGS: 00010246
RAX: 15d08b2e34b77800 RBX: 0000000000000003 RCX: ffff88804c056c80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: ffffffff813767aa R09: 0001ffffffffffff
R10: 0001ffffffffffff R11: ffff88804c056c80 R12: ffff888040b7d000
R13: ffff88804c206938 R14: ffff88804c206900 R15: ffff888041b18488
FS: 00000000022c9940(0000) GS:ffff88807ec00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9f9b122008 CR3: 0000000044b4b000 CR4: 0000000000750ee0
PKRU: 55555554
Call Trace:
__refcount_sub_and_test -origin/./include/linux/refcount.h:283 [inline]
__refcount_dec_and_test -origin/./include/linux/refcount.h:315 [inline]
refcount_dec_and_test -origin/./include/linux/refcount.h:333 [inline]
kref_put -origin/./include/linux/kref.h:64 [inline]
kobject_put+0x17b/0x180 -origin/lib/kobject.c:753
cdev_del+0x4b/0x50 -origin/fs/char_dev.c:597
tty_unregister_device+0x99/0xd0 -origin/drivers/tty/tty_io.c:3343
gsmld_detach_gsm -origin/drivers/tty/n_gsm.c:2409 [inline]
gsmld_close+0x6c/0x140 -origin/drivers/tty/n_gsm.c:2478
tty_ldisc_close -origin/drivers/tty/tty_ldisc.c:488 [inline]
tty_ldisc_kill -origin/drivers/tty/tty_ldisc.c:636 [inline]
tty_ldisc_release+0x1b6/0x400 -origin/drivers/tty/tty_ldisc.c:809
tty_release_struct+0x19/0xb0 -origin/drivers/tty/tty_io.c:1714
tty_release+0x9ad/0xa00 -origin/drivers/tty/tty_io.c:1885
Yes, the fix makes sense. But could you elaborate in the commit log when
this happens? I only wonder how real this is. I assume you inject faults
to allocations?
Reported-and-tested-by: Hao Sun <sunhao...@gmail.com>
Cc: Jiri Slaby <jsl...@suse.cz>
Use my MAINTAINERS e-mail please.
Signed-off-by: Hillf Danton <hdan...@sina.com>
---
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2384,8 +2384,18 @@ static int gsmld_attach_gsm(struct tty_s
/* Don't register device 0 - this is the control channel and not
a usable tty interface */
base = mux_num_to_base(gsm); /* Base for this MUX */
- for (i = 1; i < NUM_DLCI; i++)
- tty_register_device(gsm_tty_driver, base + i, NULL);
+ for (i = 1; i < NUM_DLCI; i++) {
+ struct device *dev;
+
+ dev = tty_register_device(gsm_tty_driver,
+ base + i, NULL);
+ if (IS_ERR(dev)) {
+ for (i--; i >= 1; i--)
+ tty_unregister_device(gsm_tty_driver,
+ base + i);
+ return PTR_ERR(dev);
+ }
+ }
}
return ret;
}
--
thanks,
--
js
suse labs
