KMSAN reported the following uninit-value access issue:
=====================================================
BUG: KMSAN: uninit-value in ppp_sync_input drivers/net/ppp/ppp_synctty.c:690 [inline]
BUG: KMSAN: uninit-value in ppp_sync_receive+0xdc9/0xe70 drivers/net/ppp/ppp_synctty.c:334
ppp_sync_input drivers/net/ppp/ppp_synctty.c:690 [inline]
ppp_sync_receive+0xdc9/0xe70 drivers/net/ppp/ppp_synctty.c:334
tiocsti+0x328/0x450 drivers/tty/tty_io.c:2295
tty_ioctl+0x808/0x1920 drivers/tty/tty_io.c:2694
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0x211/0x400 fs/ioctl.c:857
__x64_sys_ioctl+0x97/0xe0 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b
Uninit was created at:
__alloc_pages+0x75d/0xe80 mm/page_alloc.c:4591
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
__page_frag_cache_refill+0x9a/0x2c0 mm/page_alloc.c:4691
page_frag_alloc_align+0x91/0x5d0 mm/page_alloc.c:4722
page_frag_alloc include/linux/gfp.h:322 [inline]
__netdev_alloc_skb+0x215/0x6d0 net/core/skbuff.c:728
netdev_alloc_skb include/linux/skbuff.h:3225 [inline]
dev_alloc_skb include/linux/skbuff.h:3238 [inline]
ppp_sync_input drivers/net/ppp/ppp_synctty.c:669 [inline]
ppp_sync_receive+0x237/0xe70 drivers/net/ppp/ppp_synctty.c:334
tiocsti+0x328/0x450 drivers/tty/tty_io.c:2295
tty_ioctl+0x808/0x1920 drivers/tty/tty_io.c:2694
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0x211/0x400 fs/ioctl.c:857
__x64_sys_ioctl+0x97/0xe0 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b
CPU: 0 PID: 12950 Comm: syz-executor.1 Not tainted 6.6.0-14500-g1c41041124bd #10
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc38 04/01/2014
=====================================================
ppp_sync_input() checks the first 2 bytes of the data are PPP_ALLSTATIONS
and PPP_UI. However, if the data length is 1 and the first byte is
PPP_ALLSTATIONS, an access to an uninitialized value occurs when checking
PPP_UI. This patch resolves this issue by checking the data length.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Shigeru Yoshida <syoshida@xxxxxxxxxx>
---
drivers/net/ppp/ppp_synctty.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ppp/ppp_synctty.c b/drivers/net/ppp/ppp_synctty.c
index ebcdffdf4f0e..ea261a628786 100644
--- a/drivers/net/ppp/ppp_synctty.c
+++ b/drivers/net/ppp/ppp_synctty.c
@@ -687,7 +687,7 @@ ppp_sync_input(struct syncppp *ap, const u8 *buf, const u8 *flags, int count)
/* strip address/control field if present */
p = skb->data;
- if (p[0] == PPP_ALLSTATIONS && p[1] == PPP_UI) {
+ if (skb->len >= 2 && p[0] == PPP_ALLSTATIONS && p[1] == PPP_UI) {
/* chop off address/control */
if (skb->len < 3)
goto err;
--
2.41.0
