can: xilinx_can: xcan_write_frame(): fix use-after-free of transmitted SKB

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: can: xilinx_can: xcan_write_frame(): fix use-after-free of transmitted SKB can_put_echo_skb() takes ownership of the SKB and it may be freed during or after the call. However, xilinx_can xcan_write_frame() keeps using SKB after the call. Fix that by only calling can_put_echo_skb() after the code is done touching the SKB. The tx_lock is held for the entire xcan_write_frame() execution and also on the can_get_echo_skb() side so the order of operations does not matter. An earlier fix commit 3d3c817c3a40 ("can: xilinx_can: Fix usage of skb memory") did not move the can_put_echo_skb() call far enough. [mkl: add "commit" in front of sha1 in patch description] [mkl: fix indention]

References

• https://git.kernel.org/stable/c/e202ffd9e54538ef67ec301ebd6d9da4823466c9
• https://git.kernel.org/stable/c/1139321161a3ba5e45e61e0738b37f42f20bc57a
• https://git.kernel.org/stable/c/94b050726288a56a6b8ff55aa641f2fedbd3b44c
• https://git.kernel.org/stable/c/725b33deebd6e4c96fe7893f384510a54258f28f
• https://git.kernel.org/stable/c/668cc1e3bb21101d074e430de1b7ba8fd10189e7
• https://git.kernel.org/stable/c/ef79f00be72bd81d2e1e6f060d83cf7e425deee4