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wifi: cfg80211: fix UBSAN noise in cfg80211_wext_siwscan()

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Looking at https://syzkaller.appspot.com/bug?extid=1a3986bbd3169c307819
and running reproducer with CONFIG_UBSAN_BOUNDS, I've noticed the
following:

[ T4985] UBSAN: array-index-out-of-bounds in net/wireless/scan.c:3479:25
[ T4985] index 164 is out of range for type 'struct ieee80211_channel *[]'
<...skipped...>
[ T4985] Call Trace:
[ T4985]  <TASK>
[ T4985]  dump_stack_lvl+0x1c2/0x2a0
[ T4985]  ? __pfx_dump_stack_lvl+0x10/0x10
[ T4985]  ? __pfx__printk+0x10/0x10
[ T4985]  __ubsan_handle_out_of_bounds+0x127/0x150
[ T4985]  cfg80211_wext_siwscan+0x11a4/0x1260
<...the rest is not too useful...>

Even if we do 'creq->n_channels = n_channels' before 'creq->ssids =
(void *)&creq->channels[n_channels]', UBSAN treats the latter as
off-by-one error. Fix this by using pointer arithmetic rather than
an expression with explicit array indexing and use convenient
'struct_size()' to simplify the math here and in 'kzalloc()' above.

Fixes: 5ba63533bb ("cfg80211: fix alignment problem in scan request")
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Reviewed-by: Kees Cook <kees@kernel.org>
Link: https://patch.msgid.link/20240905150400.126386-1-dmantipov@yandex.ru
[fix coding style for multi-line calculation]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Dmitry Antipov 2024-09-05 18:04:00 +03:00 committed by Johannes Berg
parent 43b7724487
commit a26a5107bc
1 changed files with 3 additions and 3 deletions
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6
net/wireless/scan.c
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@ -3467,8 +3467,8 @@ int cfg80211_wext_siwscan(struct net_device *dev,
n_channels = ieee80211_get_num_supported_channels(wiphy);
}
creq = kzalloc(sizeof(*creq) + sizeof(struct cfg80211_ssid) +
n_channels * sizeof(void *),
creq = kzalloc(struct_size(creq, channels, n_channels) +
sizeof(struct cfg80211_ssid),
GFP_ATOMIC);
if (!creq)
return -ENOMEM;
@ -3476,7 +3476,7 @@ int cfg80211_wext_siwscan(struct net_device *dev,
creq->wiphy = wiphy;
creq->wdev = dev->ieee80211_ptr;
/* SSIDs come after channels */
creq->ssids = (void *)&creq->channels[n_channels];
creq->ssids = (void *)creq + struct_size(creq, channels, n_channels);
creq->n_channels = n_channels;
creq->n_ssids = 1;
creq->scan_start = jiffies;