[Devel] [PATCH vz10 07/24] blk-cbt: don't WARN on a user-supplied ABI version mismatch

[Konstantin Khorenko]

blk_cbt_ioctl() reads abi_version straight from the ioctl argument and
WARN_ONCE()s if it does not match CBT_ABI_VERSION. The value is fully
userspace-controlled, so any process issuing a BLKCBT* ioctl with a
stale/newer struct taints the kernel, dumps a backtrace, and can panic a
host that runs with panic_on_warn. Downgrade to pr_warn_ratelimited();
the -EOPNOTSUPP return is the actual contract.

Fixes: 6e42f62a2c88 ("block/blk-cbt: introduce ABI versioning")
Feature: cbt: changed block tracking (for backup)
https://virtuozzo.atlassian.net/browse/VSTOR-137234
Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
 block/blk-cbt.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-cbt.c b/block/blk-cbt.c
index 90219f58f1ae..91a888770411 100644
--- a/block/blk-cbt.c
+++ b/block/blk-cbt.c
@@ -1093,8 +1093,8 @@ int blk_cbt_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
 		return -EFAULT;
 
 	if (abi_version != CBT_ABI_VERSION) {
-		WARN_ONCE(1, "blk-cbt ABI mimatch: kernel has %d, userspace uses %d",
-			  CBT_ABI_VERSION, abi_version);
+		pr_warn_ratelimited("blk-cbt: ABI mismatch: kernel has %d, userspace uses %d\n",
+				    CBT_ABI_VERSION, abi_version);
 		return -EOPNOTSUPP;
 	}
 
-- 
2.47.1