[PATCH net-next] ethtool: prevent endless loop if eeprom size is smaller than announced

It shouldn't happen, but can happen that readable eeprom size is smaller
than announced. Then we would be stuck in an endless loop here because
after reaching the actual end reads return eeprom.len = 0. I faced this
issue when making a mistake in driver development. Detect this scenario
and return an error.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 net/ethtool/ioctl.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index f2abc3152..999e2a6be 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c

@@ -1537,6 +1537,10 @@ static int ethtool_get_any_eeprom(struct net_device *dev, void __user *useraddr,
 		ret = getter(dev, &eeprom, data);
 		if (ret)
 			break;
+		if (!eeprom.len) {
+			ret = -EIO;
+			break;
+		}
 		if (copy_to_user(userbuf, data, eeprom.len)) {
 			ret = -EFAULT;
 			break;

-- 
2.33.0

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Mon, 13 Sep 2021 21:58:26 +0200 you wrote:

It shouldn't happen, but can happen that readable eeprom size is smaller
than announced. Then we would be stuck in an endless loop here because
after reaching the actual end reads return eeprom.len = 0. I faced this
issue when making a mistake in driver development. Detect this scenario
and return an error.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>

[...]

Here is the summary with links:
  - [net-next] ethtool: prevent endless loop if eeprom size is smaller than announced
    https://git.kernel.org/netdev/net-next/c/b9bbc4c1debc

You are awesome, thank you!
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