4.17-stable review patch. If anyone has any objections, please let me know.
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From: Andrey Ryabinin aryabinin@virtuozzo.com
[ Upstream commit 2045cdfa1b40d66f126f3fd05604fc7c754f0022 ]
Loading the nf_conntrack module with doubled hashsize parameter, i.e. modprobe nf_conntrack hashsize=12345 hashsize=12345 causes NULL-ptr deref.
If 'hashsize' specified twice, the nf_conntrack_set_hashsize() function will be called also twice. The first nf_conntrack_set_hashsize() call will set the 'nf_conntrack_htable_size' variable:
nf_conntrack_set_hashsize() ... /* On boot, we can set this without any fancy locking. */ if (!nf_conntrack_htable_size) return param_set_uint(val, kp);
But on the second invocation, the nf_conntrack_htable_size is already set, so the nf_conntrack_set_hashsize() will take a different path and call the nf_conntrack_hash_resize() function. Which will crash on the attempt to dereference 'nf_conntrack_hash' pointer:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 RIP: 0010:nf_conntrack_hash_resize+0x255/0x490 [nf_conntrack] Call Trace: nf_conntrack_set_hashsize+0xcd/0x100 [nf_conntrack] parse_args+0x1f9/0x5a0 load_module+0x1281/0x1a50 __se_sys_finit_module+0xbe/0xf0 do_syscall_64+0x7c/0x390 entry_SYSCALL_64_after_hwframe+0x49/0xbe
Fix this, by checking !nf_conntrack_hash instead of !nf_conntrack_htable_size. nf_conntrack_hash will be initialized only after the module loaded, so the second invocation of the nf_conntrack_set_hashsize() won't crash, it will just reinitialize nf_conntrack_htable_size again.
Signed-off-by: Andrey Ryabinin aryabinin@virtuozzo.com Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/netfilter/nf_conntrack_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -1972,7 +1972,7 @@ int nf_conntrack_set_hashsize(const char return -EOPNOTSUPP;
/* On boot, we can set this without any fancy locking. */ - if (!nf_conntrack_htable_size) + if (!nf_conntrack_hash) return param_set_uint(val, kp);
rc = kstrtouint(val, 0, &hashsize);