On Fri, Dec 13, 2024 at 11:44:22AM +0800, haixiao.yan.cn@eng.windriver.com wrote:

From: Nathan Lynch <redacted>

[ Upstream commit 0974d03eb479384466d828d65637814bee6b26d7 ]

Smatch warns:

  arch/powerpc/kernel/rtas.c:1932 __do_sys_rtas() warn: potential
  spectre issue 'args.args' [r] (local cap)

The 'nargs' and 'nret' locals come directly from a user-supplied
buffer and are used as indexes into a small stack-based array and as
inputs to copy_to_user() after they are subject to bounds checks.

Use array_index_nospec() after the bounds checks to clamp these values
for speculative execution.

Signed-off-by: Nathan Lynch <redacted>
Reported-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240530-sys_rtas-nargs-nret-v1-1-129acddd4d89@linux.ibm.com
Signed-off-by: Haixiao Yan <redacted>
---
This commit is backporting 0974d03eb479 to the branch linux-5.15.y to
solve the CVE-2024-46774.

Now deleted, please see:
	https://lore.kernel.org/r/2024121322-conjuror-gap-b542@gregkh (local)
for what you all need to do, TOGETHER, to get this fixed and so that I
can accept patches from your company in the future.

thanks,

greg k-h