SUNRPC: Fix the svc_deferred_event trace class

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: SUNRPC: Fix the svc_deferred_event trace class Fix a NULL deref crash that occurs when an svc_rqst is deferred while the sunrpc tracing subsystem is enabled. svc_revisit() sets dr->xprt to NULL, so it can't be relied upon in the tracepoint to provide the remote's address. Unfortunately we can't revert the "svc_deferred_class" hunk in commit ece200ddd54b ("sunrpc: Save remote presentation address in svc_xprt for trace events") because there is now a specific check of event format specifiers for unsafe dereferences. The warning that check emits is: event svc_defer_recv has unsafe dereference of argument 1 A "%pISpc" format specifier with a "struct sockaddr *" is indeed flagged by this check. Instead, take the brute-force approach used by the svcrdma_qp_error tracepoint. Convert the dr::addr field into a presentation address in the TP_fast_assign() arm of the trace event, and store that as a string. This fix can be backported to -stable kernels. In the meantime, commit c6ced22997ad ("tracing: Update print fmt check to handle new __get_sockaddr() macro") is now in v5.18, so this wonky fix can be replaced with __sockaddr() and friends properly during the v5.19 merge window.

References

• https://git.kernel.org/stable/c/85ee17ca21cf92989e8c923e3ea4514c291e9d38
• https://git.kernel.org/stable/c/726ae7300fcc25fefa46d188cc07eb16dc908f9e
• https://git.kernel.org/stable/c/c2456f470eea3bd06574d988bf6089e7c3f4c5cc
• https://git.kernel.org/stable/c/4d5004451ab2218eab94a30e1841462c9316ba19