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Subject[PATCH 4.4 183/190] ip6_gre: better validate user provided tunnel names
4.4-stable review patch.  If anyone has any objections, please let me know.


From: Eric Dumazet <>

[ Upstream commit 5f42df013b8bc1b6511af7a04bf93b014884ae2a ]

Use dev_valid_name() to make sure user does not provide illegal
device name.

syzbot caught the following bug :

BUG: KASAN: stack-out-of-bounds in strlcpy include/linux/string.h:300 [inline]
BUG: KASAN: stack-out-of-bounds in ip6gre_tunnel_locate+0x334/0x860 net/ipv6/ip6_gre.c:339
Write of size 20 at addr ffff8801afb9f7b8 by task syzkaller851048/4466

CPU: 1 PID: 4466 Comm: syzkaller851048 Not tainted 4.16.0+ #1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x1b9/0x29f lib/dump_stack.c:53
print_address_description+0x6c/0x20b mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0xac/0x2f5 mm/kasan/report.c:412
check_memory_region_inline mm/kasan/kasan.c:260 [inline]
check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
memcpy+0x37/0x50 mm/kasan/kasan.c:303
strlcpy include/linux/string.h:300 [inline]
ip6gre_tunnel_locate+0x334/0x860 net/ipv6/ip6_gre.c:339
ip6gre_tunnel_ioctl+0x69d/0x12e0 net/ipv6/ip6_gre.c:1195
dev_ifsioc+0x43e/0xb90 net/core/dev_ioctl.c:334
dev_ioctl+0x69a/0xcc0 net/core/dev_ioctl.c:525
sock_ioctl+0x47e/0x680 net/socket.c:1015
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x1cf/0x1650 fs/ioctl.c:684
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
SYSC_ioctl fs/ioctl.c:708 [inline]
SyS_ioctl+0x24/0x30 fs/ioctl.c:706
do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287

Fixes: c12b395a4664 ("gre: Support GRE over IPv6")
Signed-off-by: Eric Dumazet <>
Reported-by: syzbot <>
Signed-off-by: David S. Miller <>
Signed-off-by: Greg Kroah-Hartman <>
net/ipv6/ip6_gre.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -320,11 +320,13 @@ static struct ip6_tnl *ip6gre_tunnel_loc
if (t || !create)
return t;

- if (parms->name[0])
+ if (parms->name[0]) {
+ if (!dev_valid_name(parms->name))
+ return NULL;
strlcpy(name, parms->name, IFNAMSIZ);
- else
+ } else {
strcpy(name, "ip6gre%d");
+ }
dev = alloc_netdev(sizeof(*t), name, NET_NAME_UNKNOWN,
if (!dev)

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