tty: Fix GPF in flush_to_ldisc()
commit 9ce119f3 upstream. A line discipline which does not define a receive_buf() method can can cause a GPF if data is ever received [1]. Oddly, this was known to the author of n_tracesink in 2011, but never fixed. [1] GPF report BUG: unable to handle kernel NULL pointer dereference at (null) IP: [< (null)>] (null) PGD 3752d067 PUD 37a7b067 PMD 0 Oops: 0010 [#1] SMP KASAN Modules linked in: CPU: 2 PID: 148 Comm: kworker/u10:2 Not tainted 4.4.0-rc2+ #51 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Workqueue: events_unbound flush_to_ldisc task: ffff88006da94440 ti: ffff88006db60000 task.ti: ffff88006db60000 RIP: 0010:[<0000000000000000>] [< (null)>] (null) RSP: 0018:ffff88006db67b50 EFLAGS: 00010246 RAX: 0000000000000102 RBX: ffff88003ab32f88 RCX: 0000000000000102 RDX: 0000000000000000 RSI: ffff88003ab330a6 RDI: ffff88003aabd388 RBP: ffff88006db67c48 R08: ffff88003ab32f9c R09: ffff88003ab31fb0 R10: ffff88003ab32fa8 R11: 0000000000000000 R12: dffffc0000000000 R13: ffff88006db67c20 R14: ffffffff863df820 R15: ffff88003ab31fb8 FS: 0000000000000000(0000) GS:ffff88006dc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 0000000000000000 CR3: 0000000037938000 CR4: 00000000000006e0 Stack: ffffffff829f46f1 ffff88006da94bf8 ffff88006da94bf8 0000000000000000 ffff88003ab31fb0 ffff88003aabd438 ffff88003ab31ff8 ffff88006430fd90 ffff88003ab32f9c ffffed0007557a87 1ffff1000db6cf78 ffff88003ab32078 Call Trace: [<ffffffff8127cf91>] process_one_work+0x8f1/0x17a0 kernel/workqueue.c:2030 [<ffffffff8127df14>] worker_thread+0xd4/0x1180 kernel/workqueue.c:2162 [<ffffffff8128faaf>] kthread+0x1cf/0x270 drivers/block/aoe/aoecmd.c:1302 [<ffffffff852a7c2f>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:468 Code: Bad RIP value. RIP [< (null)>] (null) RSP <ffff88006db67b50> CR2: 0000000000000000 ---[ end trace a587f8947e54d6ea ]--- Reported-by:Dmitry Vyukov <dvyukov@google.com> Signed-off-by:
Peter Hurley <peter@hurleysoftware.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org> [bwh: Backported to 3.2: adjust context] Signed-off-by:
Ben Hutchings <ben@decadent.org.uk> (cherry picked from commit b23324ff) [wt: applied to drivers/char/tty_buffer.c instead] Signed-off-by:
Willy Tarreau <w@1wt.eu>
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