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x86/kexec: Fix bug with call depth tracking

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commit 93c1800b3799f17375989b0daf76497dd3e80922 upstream.

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: 5d8213864ade ("x86/retbleed: Add SKL return thunk")
Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/20240603083036.637-1-bp@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
David Kaplan 2024-06-02 13:19:09 -05:00 committed by Greg Kroah-Hartman
parent 5c0fb9cb40
commit d91ddd0508
1 changed files with 9 additions and 2 deletions
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11
arch/x86/kernel/machine_kexec_64.c
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@ -298,8 +298,15 @@ 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)
@ -361,7 +368,7 @@ 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)