1e9cb763e9
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: <TASK> dump_stack_lvl+0x4a/0x63 dump_stack+0x10/0x16 ubsan_epilogue+0x9/0x36 __ubsan_handle_shift_out_of_bounds.cold+0x61/0x10e ? __const_udelay+0x43/0x50 ena_delay_exponential_backoff_us.cold+0x16/0x1e [ena] wait_for_reset_state+0x54/0xa0 [ena] ena_com_dev_reset+0xc8/0x110 [ena] ena_down+0x3fe/0x480 [ena] ena_destroy_device+0xeb/0xf0 [ena] ena_fw_reset_device+0x30/0x50 [ena] process_one_work+0x22b/0x3d0 worker_thread+0x4d/0x3f0 ? process_one_work+0x3d0/0x3d0 kthread+0x12a/0x150 ? set_kthread_struct+0x50/0x50 ret_from_fork+0x22/0x30 </TASK> 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. Cc: stable@vger.kernel.org Fixes: 4bb7f4cf60e3 ("net: ena: reduce driver load time") Signed-off-by: Krister Johansen <kjlx@templeofstupid.com> Reviewed-by: Leon Romanovsky <leonro@nvidia.com> Reviewed-by: Shay Agroskin <shayagr@amazon.com> Link: https://lore.kernel.org/r/20230711013621.GE1926@templeofstupid.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.