In the Linux kernel, the following vulnerability has been resolved:

can: mcp251xfd: fix infinite loop when xmit fails

When the mcp251xfd_start_xmit() function fails, the driver stops
processing messages, and the interrupt routine does not return,
running indefinitely even after killing the running application.

Error messages:
[  441.298819] mcp251xfd spi2.0 can0: ERROR in mcp251xfd_start_xmit: -16
[  441.306498] mcp251xfd spi2.0 can0: Transmit Event FIFO buffer not empty. (seq=0x000017c7, tef_tail=0x000017cf, tef_head=0x000017d0, tx_head=0x000017d3).
... and repeat forever.

The issue can be triggered when multiple devices share the same SPI
interface. And there is concurrent access to the bus.

The problem occurs because tx_ring->head increments even if
mcp251xfd_start_xmit() fails. Consequently, the driver skips one TX
package while still expecting a response in
mcp251xfd_handle_tefif_one().

Resolve the issue by starting a workqueue to write the tx obj
synchronously if err = -EBUSY. In case of another error, decrement
tx_ring->head, remove skb from the echo stack, and drop the message.

[mkl: use more imperative wording in patch description]

kernel.org https://git.kernel.org/stable/c/3e72558c1711d524e3150103739ddd06650e291b [No types assigned]

kernel.org https://git.kernel.org/stable/c/6c6b4afa59c2fb4d1759235f866d8caed2aa4729 [No types assigned]

kernel.org https://git.kernel.org/stable/c/d8fb63e46c884c898a38f061c2330f7729e75510 [No types assigned]

kernel.org https://git.kernel.org/stable/c/f926c022ebaabf7963bebf89a97201d66978a025 [No types assigned]