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ppp: clarify parsing of user supplied data in ppp_set_compress()

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* Split big conditional statement.
  * Check (data.length <= CCP_MAX_OPTION_LENGTH) only once.
  * Don't read ccp_option[1] if not initialised.

Reading uninitialised ccp_option[1] was harmless, because this could
only happen when data.length was 0 or 1. So even then, we couldn't pass
the (ccp_option[1] < 2 || ccp_option[1] > data.length) test anyway.

Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Guillaume Nault 2016-02-23 13:59:43 +01:00 committed by David S. Miller
parent 4fee7dab07
commit 555d5b70f1
1 changed files with 7 additions and 5 deletions
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12
drivers/net/ppp/ppp_generic.c
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@ -2429,13 +2429,15 @@ ppp_set_compress(struct ppp *ppp, unsigned long arg)
unsigned char ccp_option[CCP_MAX_OPTION_LENGTH];
err = -EFAULT;
if (copy_from_user(&data, (void __user *) arg, sizeof(data)) ||
(data.length <= CCP_MAX_OPTION_LENGTH &&
copy_from_user(ccp_option, (void __user *) data.ptr, data.length)))
if (copy_from_user(&data, (void __user *) arg, sizeof(data)))
goto out;
if (data.length > CCP_MAX_OPTION_LENGTH)
goto out;
if (copy_from_user(ccp_option, (void __user *) data.ptr, data.length))
goto out;
err = -EINVAL;
if (data.length > CCP_MAX_OPTION_LENGTH ||
ccp_option[1] < 2 || ccp_option[1] > data.length)
if (data.length < 2 || ccp_option[1] < 2 || ccp_option[1] > data.length)
goto out;
cp = try_then_request_module(