On Wed, Jan 24, 2024 at 11:14 AM <kovalev(a)altlinux.org> wrote:
From: Vasiliy Kovalev <kovalev(a)altlinux.org>
After unloading the module, an instance continues to exist that accesses
outdated memory addresses.
To prevent this, the dump_pdp_en flag has been added, which blocks the
dump of pdp contexts by a false value. And only after these checks can
the net_generic() function be called.
These errors were found using the syzkaller program:
Syzkaller hit 'general protection fault in gtp_genl_dump_pdp' bug.
gtp: GTP module loaded (pdp ctx size 104 bytes)
gtp: GTP module unloaded
general protection fault, probably for non-canonical address
0xdffffc0000000001:0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 PID: 2782 Comm: syz-executor139 Not tainted 5.10.200-std-def-alt1 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-alt1
RIP: 0010:gtp_genl_dump_pdp+0x1b1/0x790 [gtp]
...
Call Trace:
genl_lock_dumpit+0x6b/0xa0 net/netlink/genetlink.c:623
netlink_dump+0x575/0xc70 net/netlink/af_netlink.c:2271
__netlink_dump_start+0x64e/0x910 net/netlink/af_netlink.c:2376
genl_family_rcv_msg_dumpit+0x2b8/0x310 net/netlink/genetlink.c:686
genl_family_rcv_msg net/netlink/genetlink.c:780 [inline]
genl_rcv_msg+0x450/0x5a0 net/netlink/genetlink.c:800
netlink_rcv_skb+0x150/0x440 net/netlink/af_netlink.c:2497
genl_rcv+0x29/0x40 net/netlink/genetlink.c:811
netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline]
netlink_unicast+0x54e/0x800 net/netlink/af_netlink.c:1348
netlink_sendmsg+0x914/0xe00 net/netlink/af_netlink.c:1916
sock_sendmsg_nosec net/socket.c:651 [inline]
__sock_sendmsg+0x159/0x190 net/socket.c:663
____sys_sendmsg+0x712/0x870 net/socket.c:2376
___sys_sendmsg+0xf8/0x170 net/socket.c:2430
__sys_sendmsg+0xea/0x1b0 net/socket.c:2459
do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x62/0xc7
RIP: 0033:0x7f2ea16c2d49
Fixes: 94a6d9fb88df ("gtp: fix wrong condition in gtp_genl_dump_pdp()")
Signed-off-by: Vasiliy Kovalev <kovalev(a)altlinux.org>
---
drivers/net/gtp.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index 477b4d4f860bd3..3fc4639711cd83 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -1675,6 +1675,8 @@ static int gtp_genl_get_pdp(struct sk_buff *skb, struct genl_info
*info)
return err;
}
+static bool dump_pdp_en;
+
Hmm, it seems there is a missing try_module_get() somewhere...
__netlink_dump_start() does one, so perhaps we reach __netlink_dump_start()
with a NULL in control->module ?