4.4-stable patches

added patches:
	tty-prevent-ldisc-drivers-from-re-using-stale-tty-fields.patch

diff --git a/queue-4.4/series b/queue-4.4/series
index 5fffc5ef28c1594029619f24ee68e71a4402e112..3b9e550195d5344b2a7c565e91eff960d177846c 100644 (file)
--- a/queue-4.4/series
+++ b/queue-4.4/series
@@ -14,3 +14,4 @@ sock-fix-sendmmsg-for-partial-sendmsg.patch
 net-__skb_flow_dissect-must-cap-its-return-value.patch
 ipv4-use-new_gw-for-redirect-neigh-lookup.patch
 tcp-take-care-of-truncations-done-by-sk_filter.patch
+tty-prevent-ldisc-drivers-from-re-using-stale-tty-fields.patch

diff --git a/queue-4.4/tty-prevent-ldisc-drivers-from-re-using-stale-tty-fields.patch b/queue-4.4/tty-prevent-ldisc-drivers-from-re-using-stale-tty-fields.patch
new file mode 100644 (file)
index 0000000..49a4b98
--- /dev/null
+++ b/queue-4.4/tty-prevent-ldisc-drivers-from-re-using-stale-tty-fields.patch
@@ -0,0 +1,79 @@
+From dd42bf1197144ede075a9d4793123f7689e164bc Mon Sep 17 00:00:00 2001
+From: Peter Hurley <peter@hurleysoftware.com>
+Date: Fri, 27 Nov 2015 14:30:21 -0500
+Subject: tty: Prevent ldisc drivers from re-using stale tty fields
+
+From: Peter Hurley <peter@hurleysoftware.com>
+
+commit dd42bf1197144ede075a9d4793123f7689e164bc upstream.
+
+Line discipline drivers may mistakenly misuse ldisc-related fields
+when initializing. For example, a failure to initialize tty->receive_room
+in the N_GIGASET_M101 line discipline was recently found and fixed [1].
+Now, the N_X25 line discipline has been discovered accessing the previous
+line discipline's already-freed private data [2].
+
+Harden the ldisc interface against misuse by initializing revelant
+tty fields before instancing the new line discipline.
+
+[1]
+    commit fd98e9419d8d622a4de91f76b306af6aa627aa9c
+    Author: Tilman Schmidt <tilman@imap.cc>
+    Date:   Tue Jul 14 00:37:13 2015 +0200
+
+    isdn/gigaset: reset tty->receive_room when attaching ser_gigaset
+
+[2] Report from Sasha Levin <sasha.levin@oracle.com>
+    [  634.336761] ==================================================================
+    [  634.338226] BUG: KASAN: use-after-free in x25_asy_open_tty+0x13d/0x490 at addr ffff8800a743efd0
+    [  634.339558] Read of size 4 by task syzkaller_execu/8981
+    [  634.340359] =============================================================================
+    [  634.341598] BUG kmalloc-512 (Not tainted): kasan: bad access detected
+    ...
+    [  634.405018] Call Trace:
+    [  634.405277] dump_stack (lib/dump_stack.c:52)
+    [  634.405775] print_trailer (mm/slub.c:655)
+    [  634.406361] object_err (mm/slub.c:662)
+    [  634.406824] kasan_report_error (mm/kasan/report.c:138 mm/kasan/report.c:236)
+    [  634.409581] __asan_report_load4_noabort (mm/kasan/report.c:279)
+    [  634.411355] x25_asy_open_tty (drivers/net/wan/x25_asy.c:559 (discriminator 1))
+    [  634.413997] tty_ldisc_open.isra.2 (drivers/tty/tty_ldisc.c:447)
+    [  634.414549] tty_set_ldisc (drivers/tty/tty_ldisc.c:567)
+    [  634.415057] tty_ioctl (drivers/tty/tty_io.c:2646 drivers/tty/tty_io.c:2879)
+    [  634.423524] do_vfs_ioctl (fs/ioctl.c:43 fs/ioctl.c:607)
+    [  634.427491] SyS_ioctl (fs/ioctl.c:622 fs/ioctl.c:613)
+    [  634.427945] entry_SYSCALL_64_fastpath (arch/x86/entry/entry_64.S:188)
+
+Cc: Tilman Schmidt <tilman@imap.cc>
+Cc: Sasha Levin <sasha.levin@oracle.com>
+Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
+Cc: Jiri Slaby <jslaby@suse.cz>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ drivers/tty/tty_ldisc.c |    7 +++++++
+ 1 file changed, 7 insertions(+)
+
+--- a/drivers/tty/tty_ldisc.c
++++ b/drivers/tty/tty_ldisc.c
+@@ -417,6 +417,10 @@ EXPORT_SYMBOL_GPL(tty_ldisc_flush);
+  *    they are not on hot paths so a little discipline won't do
+  *    any harm.
+  *
++ *    The line discipline-related tty_struct fields are reset to
++ *    prevent the ldisc driver from re-using stale information for
++ *    the new ldisc instance.
++ *
+  *    Locking: takes termios_rwsem
+  */
+ 
+@@ -425,6 +429,9 @@ static void tty_set_termios_ldisc(struct
+       down_write(&tty->termios_rwsem);
+       tty->termios.c_line = num;
+       up_write(&tty->termios_rwsem);
++
++      tty->disc_data = NULL;
++      tty->receive_room = 0;
+ }
+ 
+ /**