Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
net: ena: fix shift-out-of-bounds in exponential backoff
The ENA adapters on our instances occasionally reset. Once recently logged a UBSAN failure to console in the process:
UBSAN: shift-out-of-bounds in build/linux/drivers/net/ethernet/amazon/ena/ena_com.c:540:13
shift exponent 32 is too large for 32-bit type ‘unsigned int’
CPU: 28 PID: 70012 Comm: kworker/u72:2 Kdump: loaded not tainted 5.15.117
Hardware name: Amazon EC2 c5d.9xlarge/, BIOS 1.0 10/16/2017
Workqueue: ena ena_fw_reset_device [ena]
Call Trace:
Apparently, the reset delays are getting so large they can trigger a UBSAN panic.
Looking at the code, the current timeout is capped at 5000us. Using a base value of 100us, the current code will overflow after (1«29). Even at values before 32, this function wraps around, perhaps unintentionally.
Cap the value of the exponent used for this backoff at (1«16) which is larger than currently necessary, but large enough to support bigger values in the future.
Details
- Affected product:
- AlmaLinux 9.2 ESU
- Affected packages:
- kernel @ 5.14.0
In the Linux kernel, the following vulnerability has been resolved:
net: ena: fix shift-out-of-bounds in exponential backoff
The ENA adapters on our instances occasionally reset. Once recently logged a UBSAN failure to console in the process:
UBSAN: shift-out-of-bounds in build/linux/drivers/net/ethernet/amazon/ena/ena_com.c:540:13
shift exponent 32 is too large for 32-bit type ‘unsigned int’
CPU: 28 PID: 70012 Comm: kworker/u72:2 Kdump: loaded not tainted 5.15.117
Hardware name: Amazon EC2 c5d.9xlarge/, BIOS 1.0 10/16/2017
Workqueue: ena ena_fw_reset_device [ena]
Call Trace:
Apparently, the reset delays are getting so large they can trigger a UBSAN panic.
Looking at the code, the current timeout is capped at 5000us. Using a base value of 100us, the current code will overflow after (1«29). Even at values before 32, this function wraps around, perhaps unintentionally.
Cap the value of the exponent used for this backoff at (1«16) which is larger than currently necessary, but large enough to support bigger values in the future.