Commit 93c1800b authored by David Kaplan's avatar David Kaplan Committed by Borislav Petkov (AMD)
Browse files

x86/kexec: Fix bug with call depth tracking 



The call to cc_platform_has() triggers a fault and system crash if call depth
tracking is active because the GS segment has been reset by load_segments() and
GS_BASE is now 0 but call depth tracking uses per-CPU variables to operate.

Call cc_platform_has() earlier in the function when GS is still valid.

  [ bp: Massage. ]

Fixes: 5d821386 ("x86/retbleed: Add SKL return thunk")
Signed-off-by: default avatarDavid Kaplan <david.kaplan@amd.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/20240603083036.637-1-bp@kernel.org
parent c3f38fa6

arch/x86/kernel/machine_kexec_64.c

+9 −2
Original line number Diff line number Diff line
@@ -295,8 +295,15 @@ void machine_kexec_cleanup(struct kimage *image) 
void machine_kexec(struct kimage *image)

{

	unsigned long page_list[PAGES_NR];

	void *control_page;

	unsigned int host_mem_enc_active;

	int save_ftrace_enabled;

	void *control_page;



	/*

	 * This must be done before load_segments() since if call depth tracking

	 * is used then GS must be valid to make any function calls.

	 */

	host_mem_enc_active = cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT);



#ifdef CONFIG_KEXEC_JUMP

	if (image->preserve_context)
@@ -358,7 +365,7 @@ void machine_kexec(struct kimage *image) 
				       (unsigned long)page_list,

				       image->start,

				       image->preserve_context,

				       cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT));

				       host_mem_enc_active);



#ifdef CONFIG_KEXEC_JUMP

	if (image->preserve_context)