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Subject[PATCH 4.14 33/61] netfilter: nf_tables: fix NULL-ptr in nf_tables_dump_obj()
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Taehee Yoo <ap420073@gmail.com>

commit 360cc79d9d299ce297b205508276285ceffc5fa8 upstream.

The table field in nft_obj_filter is not an array. In order to check
tablename, we should check if the pointer is set.

Test commands:

%nft add table ip filter
%nft add counter ip filter ct1
%nft reset counters

Splat looks like:

[ 306.510504] kasan: CONFIG_KASAN_INLINE enabled
[ 306.516184] kasan: GPF could be caused by NULL-ptr deref or user memory access
[ 306.524775] general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
[ 306.528284] Modules linked in: nft_objref nft_counter nf_tables nfnetlink ip_tables x_tables
[ 306.528284] CPU: 0 PID: 1488 Comm: nft Not tainted 4.17.0-rc4+ #17
[ 306.528284] Hardware name: To be filled by O.E.M. To be filled by O.E.M./Aptio CRB, BIOS 5.6.5 07/08/2015
[ 306.528284] RIP: 0010:nf_tables_dump_obj+0x52c/0xa70 [nf_tables]
[ 306.528284] RSP: 0018:ffff8800b6cb7520 EFLAGS: 00010246
[ 306.528284] RAX: 0000000000000000 RBX: ffff8800b6c49820 RCX: 0000000000000000
[ 306.528284] RDX: 0000000000000000 RSI: dffffc0000000000 RDI: ffffed0016d96e9a
[ 306.528284] RBP: ffff8800b6cb75c0 R08: ffffed00236fce7c R09: ffffed00236fce7b
[ 306.528284] R10: ffffffff9f6241e8 R11: ffffed00236fce7c R12: ffff880111365108
[ 306.528284] R13: 0000000000000000 R14: ffff8800b6c49860 R15: ffff8800b6c49860
[ 306.528284] FS: 00007f838b007700(0000) GS:ffff88011b600000(0000) knlGS:0000000000000000
[ 306.528284] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 306.528284] CR2: 00007ffeafabcf78 CR3: 00000000b6cbe000 CR4: 00000000001006f0
[ 306.528284] Call Trace:
[ 306.528284] netlink_dump+0x470/0xa20
[ 306.528284] __netlink_dump_start+0x5ae/0x690
[ 306.528284] ? nf_tables_getobj+0x1b3/0x740 [nf_tables]
[ 306.528284] nf_tables_getobj+0x2f5/0x740 [nf_tables]
[ 306.528284] ? nft_obj_notify+0x100/0x100 [nf_tables]
[ 306.528284] ? nf_tables_getobj+0x740/0x740 [nf_tables]
[ 306.528284] ? nf_tables_dump_flowtable_done+0x70/0x70 [nf_tables]
[ 306.528284] ? nft_obj_notify+0x100/0x100 [nf_tables]
[ 306.528284] nfnetlink_rcv_msg+0x8ff/0x932 [nfnetlink]
[ 306.528284] ? nfnetlink_rcv_msg+0x216/0x932 [nfnetlink]
[ 306.528284] netlink_rcv_skb+0x1c9/0x2f0
[ 306.528284] ? nfnetlink_bind+0x1d0/0x1d0 [nfnetlink]
[ 306.528284] ? debug_check_no_locks_freed+0x270/0x270
[ 306.528284] ? netlink_ack+0x7a0/0x7a0
[ 306.528284] ? ns_capable_common+0x6e/0x110
[ ... ]

Fixes: e46abbcc05aa8 ("netfilter: nf_tables: Allow table names of up to 255 chars")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/netfilter/nf_tables_api.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -4614,7 +4614,7 @@ static int nf_tables_dump_obj(struct sk_
if (idx > s_idx)
memset(&cb->args[1], 0,
sizeof(cb->args) - sizeof(cb->args[0]));
- if (filter && filter->table[0] &&
+ if (filter && filter->table &&
strcmp(filter->table, table->name))
goto cont;
if (filter &&

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