From: Vivien Didelot vivien.didelot@gmail.com
[ Upstream commit 0ee4e76937d69128a6a66861ba393ebdc2ffc8a2 ]
ethtool_get_regs() allocates a buffer of size ops->get_regs_len(), and pass it to the kernel driver via ops->get_regs() for filling.
There is no restriction about what the kernel drivers can or cannot do with the open ethtool_regs structure. They usually set regs->version and ignore regs->len or set it to the same size as ops->get_regs_len().
But if userspace allocates a smaller buffer for the registers dump, we would cause a userspace buffer overflow in the final copy_to_user() call, which uses the regs.len value potentially reset by the driver.
To fix this, make this case obvious and store regs.len before calling ops->get_regs(), to only copy as much data as requested by userspace, up to the value returned by ops->get_regs_len().
While at it, remove the redundant check for non-null regbuf.
Signed-off-by: Vivien Didelot vivien.didelot@gmail.com Reviewed-by: Michal Kubecek mkubecek@suse.cz Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/core/ethtool.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/net/core/ethtool.c +++ b/net/core/ethtool.c @@ -893,13 +893,16 @@ static int ethtool_get_regs(struct net_d return -ENOMEM; }
+ if (regs.len < reglen) + reglen = regs.len; + ops->get_regs(dev, ®s, regbuf);
ret = -EFAULT; if (copy_to_user(useraddr, ®s, sizeof(regs))) goto out; useraddr += offsetof(struct ethtool_regs, data); - if (regbuf && copy_to_user(useraddr, regbuf, regs.len)) + if (copy_to_user(useraddr, regbuf, reglen)) goto out; ret = 0;