drm/amd/display: fix a Null pointer dereference vulnerability

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: fix a Null pointer dereference vulnerability [Why] A null pointer dereference vulnerability exists in the AMD display driver's (DC module) cleanup function dc_destruct(). When display control context (dc->ctx) construction fails (due to memory allocation failure), this pointer remains NULL. During subsequent error handling when dc_destruct() is called, there's no NULL check before dereferencing the perf_trace member (dc->ctx->perf_trace), causing a kernel null pointer dereference crash. [How] Check if dc->ctx is non-NULL before dereferencing. (Updated commit text and removed unnecessary error message) (cherry picked from commit 9dd8e2ba268c636c240a918e0a31e6feaee19404)

References

• https://git.kernel.org/stable/c/0961673cc5f0055957aa46f25eb4ef6c07e00165
• https://git.kernel.org/stable/c/4ade995b9b25b3c6e8dc42c27070340f1358d8c8
• https://git.kernel.org/stable/c/1bcf63a44381691d6192872801f830ce3250e367