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netfilter: x_tables: add and use xt_check_proc_name

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commit b1d0a5d0cba4597c0394997b2d5fced3e3841b4e upstream.

recent and hashlimit both create /proc files, but only check that
name is 0 terminated.

This can trigger WARN() from procfs when name is "" or "/".
Add helper for this and then use it for both.

Cc: Eric Dumazet <eric.dumazet@gmail.com>
Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Reported-by: <syzbot+0502b00edac2a0680b61@syzkaller.appspotmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Florian Westphal 2018-03-10 01:15:45 +01:00 committed by Greg Kroah-Hartman
parent eaa0e4e1b9
commit 9aaaa409c5
4 changed files with 38 additions and 5 deletions
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2
include/linux/netfilter/x_tables.h
View File

@ -247,6 +247,8 @@ unsigned int *xt_alloc_entry_offsets(unsigned int size);
bool xt_find_jump_offset(const unsigned int *offsets,
unsigned int target, unsigned int size);
int xt_check_proc_name(const char *name, unsigned int size);
int xt_check_match(struct xt_mtchk_param *, unsigned int size, u_int8_t proto,
bool inv_proto);
int xt_check_target(struct xt_tgchk_param *, unsigned int size, u_int8_t proto,

30
net/netfilter/x_tables.c
View File

@ -366,6 +366,36 @@ textify_hooks(char *buf, size_t size, unsigned int mask, uint8_t nfproto)
return buf;
}
/**
* xt_check_proc_name - check that name is suitable for /proc file creation
*
* @name: file name candidate
* @size: length of buffer
*
* some x_tables modules wish to create a file in /proc.
* This function makes sure that the name is suitable for this
* purpose, it checks that name is NUL terminated and isn't a 'special'
* name, like "..".
*
* returns negative number on error or 0 if name is useable.
*/
int xt_check_proc_name(const char *name, unsigned int size)
{
if (name[0] == '\0')
return -EINVAL;
if (strnlen(name, size) == size)
return -ENAMETOOLONG;
if (strcmp(name, ".") == 0 ||
strcmp(name, "..") == 0 ||
strchr(name, '/'))
return -EINVAL;
return 0;
}
EXPORT_SYMBOL(xt_check_proc_name);
int xt_check_match(struct xt_mtchk_param *par,
unsigned int size, u_int8_t proto, bool inv_proto)
{

5
net/netfilter/xt_hashlimit.c
View File

@ -668,8 +668,9 @@ static int hashlimit_mt_check(const struct xt_mtchk_param *par)
if (info->cfg.gc_interval == 0 || info->cfg.expire == 0)
return -EINVAL;
if (info->name[sizeof(info->name)-1] != '\0')
return -EINVAL;
ret = xt_check_proc_name(info->name, sizeof(info->name));
if (ret)
return ret;
if (par->family == NFPROTO_IPV4) {
if (info->cfg.srcmask > 32 || info->cfg.dstmask > 32)
return -EINVAL;

6
net/netfilter/xt_recent.c
View File

@ -364,9 +364,9 @@ static int recent_mt_check(const struct xt_mtchk_param *par,
info->hit_count, XT_RECENT_MAX_NSTAMPS - 1);
return -EINVAL;
}
if (info->name[0] == '\0' ||
strnlen(info->name, XT_RECENT_NAME_LEN) == XT_RECENT_NAME_LEN)
return -EINVAL;
ret = xt_check_proc_name(info->name, sizeof(info->name));
if (ret)
return ret;
if (ip_pkt_list_tot && info->hit_count < ip_pkt_list_tot)
nstamp_mask = roundup_pow_of_two(ip_pkt_list_tot) - 1;