net/packet: check length in getsockopt() called with PACKET_HDRLEN
commit fd2c83b35752f0a8236b976978ad4658df14a59f upstream. In the case getsockopt() is called with PACKET_HDRLEN and optlen < 4 |val| remains uninitialized and the syscall may behave differently depending on its value, and even copy garbage to userspace on certain architectures. To fix this we now return -EINVAL if optlen is too small. This bug has been detected with KMSAN. Signed-off-by: Alexander Potapenko <glider@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Willy Tarreau <w@1wt.eu>
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@ -3350,6 +3350,8 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
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case PACKET_HDRLEN:
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if (len > sizeof(int))
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len = sizeof(int);
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if (len < sizeof(int))
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return -EINVAL;
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if (copy_from_user(&val, optval, len))
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return -EFAULT;
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switch (val) {
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