WARNING in nft_request_module

WARNING in nft_request_module

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    51d69817 Merge tag 'platform-drivers-x86-v5.5-3' of git://..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17645c35e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cfbb8fa33f49f9f3
dashboard link: https://syzkaller.appspot.com/bug?extid=0e63ae76d117ae1c3a01
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/  
c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11123421e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15b873fee00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0e63ae76d117ae1c3a01@syzkaller.appspotmail.com

netlink: 760 bytes leftover after parsing attributes in process  
`syz-executor332'.
------------[ cut here ]------------
truncated: 'nft-expr-0-���LMMR�~�\x1e�*�{\x7f���F��\x17��\v\vDc�\x06�H�c\x16(\x16��?V\x1c�' (len  
209)
WARNING: CPU: 1 PID: 8621 at net/netfilter/nf_tables_api.c:588  
nft_request_module+0x103/0x110 net/netfilter/nf_tables_api.c:588
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 8621 Comm: syz-executor332 Not tainted 5.5.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1fb/0x318 lib/dump_stack.c:118
  panic+0x264/0x7a9 kernel/panic.c:221
  __warn+0x209/0x210 kernel/panic.c:582
  report_bug+0x1b6/0x2f0 lib/bug.c:195
  fixup_bug arch/x86/kernel/traps.c:174 [inline]
  do_error_trap+0xda/0x440 arch/x86/kernel/traps.c:267
  do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:286
  invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:nft_request_module+0x103/0x110 net/netfilter/nf_tables_api.c:588
Code: 88 00 00 00 75 28 48 8d 65 f0 5b 41 5e 5d c3 e8 a3 3b e0 fa 48 8d 74  
24 50 48 c7 c7 e0 ba e2 88 44 89 f2 31 c0 e8 ad 47 b2 fa <0f> 0b eb c5 e8  
44 48 b2 fa 0f 1f 40 00 55 48 89 e5 41 57 41 56 41
RSP: 0018:ffffc90001ea75b0 EFLAGS: 00010246
RAX: a0c74c5486a24900 RBX: ffffffff89353700 RCX: ffff88808f06c1c0
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000282
RBP: ffffc90001ea7650 R08: ffff88808f06ca18 R09: fffffbfff13cd132
R10: fffffbfff13cd132 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff8880a3f8f168 R14: 00000000000000d1 R15: ffffffff8936d1f0
  nft_expr_type_request_module net/netfilter/nf_tables_api.c:2320 [inline]
  nft_expr_type_get net/netfilter/nf_tables_api.c:2345 [inline]
  nf_tables_expr_parse+0x308/0x9e0 net/netfilter/nf_tables_api.c:2420
  nf_tables_newrule+0xefb/0x2d90 net/netfilter/nf_tables_api.c:3037
  nfnetlink_rcv_batch net/netfilter/nfnetlink.c:433 [inline]
  nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:543 [inline]
  nfnetlink_rcv+0xecf/0x1e50 net/netfilter/nfnetlink.c:561
  netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
  netlink_unicast+0x767/0x920 net/netlink/af_netlink.c:1328
  netlink_sendmsg+0xa2c/0xd50 net/netlink/af_netlink.c:1917
  sock_sendmsg_nosec net/socket.c:639 [inline]
  sock_sendmsg net/socket.c:659 [inline]
  ____sys_sendmsg+0x4f7/0x7f0 net/socket.c:2330
  ___sys_sendmsg net/socket.c:2384 [inline]
  __sys_sendmsg+0x1ed/0x290 net/socket.c:2417
  __do_sys_sendmsg net/socket.c:2426 [inline]
  __se_sys_sendmsg net/socket.c:2424 [inline]
  __x64_sys_sendmsg+0x7f/0x90 net/socket.c:2424
  do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440619
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffeca951478 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440619
RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000005
RBP: 00000000006cb018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000004002c8 R11: 0000000000000246 R12: 0000000000401ea0
R13: 0000000000401f30 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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[PATCH nf] netfilter: nf_tables: remove WARN and add NLA_STRING upper limits

[Florian Westphal]

This WARN can trigger because some of the names fed to the module
autoload function can be of arbitrary length.

Remove the WARN and add limits for all NLA_STRING attributes.

Reported-by: syzbot+0e63ae76d117ae1c3a01@syzkaller.appspotmail.com
Fixes: 452238e8d5ffd8 ("netfilter: nf_tables: add and use helper for module autoload")
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_tables_api.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 43f05b3acd60..5a1a6632e3a6 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -22,6 +22,8 @@
 #include <net/net_namespace.h>
 #include <net/sock.h>
 
+#define NFT_MODULE_AUTOLOAD_LIMIT (MODULE_NAME_LEN - sizeof("nft-expr-255-"))
+
 static LIST_HEAD(nf_tables_expressions);
 static LIST_HEAD(nf_tables_objects);
 static LIST_HEAD(nf_tables_flowtables);
@@ -585,7 +587,7 @@ static void nft_request_module(struct net *net, const char *fmt, ...)
 	va_start(args, fmt);
 	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
 	va_end(args);
-	if (WARN(ret >= MODULE_NAME_LEN, "truncated: '%s' (len %d)", module_name, ret))
+	if (ret >= MODULE_NAME_LEN)
 		return;
 
 	mutex_unlock(&net->nft.commit_mutex);
@@ -1241,7 +1243,8 @@ static const struct nla_policy nft_chain_policy[NFTA_CHAIN_MAX + 1] = {
 				    .len = NFT_CHAIN_MAXNAMELEN - 1 },
 	[NFTA_CHAIN_HOOK]	= { .type = NLA_NESTED },
 	[NFTA_CHAIN_POLICY]	= { .type = NLA_U32 },
-	[NFTA_CHAIN_TYPE]	= { .type = NLA_STRING },
+	[NFTA_CHAIN_TYPE]	= { .type = NLA_STRING,
+				    .len = NFT_MODULE_AUTOLOAD_LIMIT },
 	[NFTA_CHAIN_COUNTERS]	= { .type = NLA_NESTED },
 	[NFTA_CHAIN_FLAGS]	= { .type = NLA_U32 },
 };
@@ -2355,7 +2358,8 @@ static const struct nft_expr_type *nft_expr_type_get(struct net *net,
 }
 
 static const struct nla_policy nft_expr_policy[NFTA_EXPR_MAX + 1] = {
-	[NFTA_EXPR_NAME]	= { .type = NLA_STRING },
+	[NFTA_EXPR_NAME]	= { .type = NLA_STRING,
+				    .len = NFT_MODULE_AUTOLOAD_LIMIT },
 	[NFTA_EXPR_DATA]	= { .type = NLA_NESTED },
 };
 
@@ -4198,7 +4202,8 @@ static const struct nla_policy nft_set_elem_policy[NFTA_SET_ELEM_MAX + 1] = {
 	[NFTA_SET_ELEM_USERDATA]	= { .type = NLA_BINARY,
 					    .len = NFT_USERDATA_MAXLEN },
 	[NFTA_SET_ELEM_EXPR]		= { .type = NLA_NESTED },
-	[NFTA_SET_ELEM_OBJREF]		= { .type = NLA_STRING },
+	[NFTA_SET_ELEM_OBJREF]		= { .type = NLA_STRING,
+					    .len = NFT_OBJ_MAXNAMELEN - 1 },
 };
 
 static const struct nla_policy nft_set_elem_list_policy[NFTA_SET_ELEM_LIST_MAX + 1] = {
-- 
2.24.1

Re: WARNING in nft_request_module

[syzbot]

syzbot has bisected this bug to:

commit 452238e8d5ffd8b77f92387519513839d4ca7379
Author: Florian Westphal <fw@strlen.de>
Date:   Wed Jul 11 11:45:10 2018 +0000

     netfilter: nf_tables: add and use helper for module autoload

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17bb83e1e00000
start commit:   51d69817 Merge tag 'platform-drivers-x86-v5.5-3' of git://..
git tree:       upstream
final crash:    https://syzkaller.appspot.com/x/report.txt?x=147b83e1e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=107b83e1e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d9290aeb7e6cf1c4
dashboard link: https://syzkaller.appspot.com/bug?extid=0e63ae76d117ae1c3a01
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16b14421e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=138473fee00000

Reported-by: syzbot+0e63ae76d117ae1c3a01@syzkaller.appspotmail.com
Fixes: 452238e8d5ff ("netfilter: nf_tables: add and use helper for module  
autoload")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Re: [PATCH nf] netfilter: nf_tables: remove WARN and add NLA_STRING upper limits

[Pablo Neira Ayuso]

On Thu, Jan 16, 2020 at 09:06:50AM +0100, Florian Westphal wrote:
> This WARN can trigger because some of the names fed to the module
> autoload function can be of arbitrary length.
> 
> Remove the WARN and add limits for all NLA_STRING attributes.

Applied, thanks.