2023-12-01 08:57:45

by Uros Bizjak

Subject: [PATCH] x86/callthunks: Correct calculation of dest address in is_callthunk()

GCC didn't warn on the invalid use of relocation destination
pointer, so the calculated destination value was applied to
the uninitialized pointer location in error.

Fixes: 17bce3b2ae2d ("x86/callthunks: Handle %rip-relative relocations in call thunk template")
Reported-by: Nathan Chancellor <[email protected]>
Closes: https://lore.kernel.org/lkml/[email protected]/
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Uros Bizjak <[email protected]>
---
arch/x86/kernel/callthunks.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c
index f5507c95e7be..c561dd481eb9 100644
--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -306,7 +306,7 @@ static bool is_callthunk(void *addr)
if (!thunks_initialized || skip_addr((void *)dest))
return false;

- *pad = dest - tmpl_size;
+ pad = (void *)(dest - tmpl_size);

memcpy(insn_buff, skl_call_thunk_template, tmpl_size);
apply_relocation(insn_buff, tmpl_size, pad,
--
2.31.1

2023-12-01 21:44:18

by Nathan Chancellor

Subject: Re: [PATCH] x86/callthunks: Correct calculation of dest address in is_callthunk()

On Fri, Dec 01, 2023 at 09:57:27AM +0100, Uros Bizjak wrote:
> GCC didn't warn on the invalid use of relocation destination
> pointer, so the calculated destination value was applied to
> the uninitialized pointer location in error.
>
> Fixes: 17bce3b2ae2d ("x86/callthunks: Handle %rip-relative relocations in call thunk template")
> Reported-by: Nathan Chancellor <[email protected]>
> Closes: https://lore.kernel.org/lkml/[email protected]/
> Cc: Ingo Molnar <[email protected]>
> Signed-off-by: Uros Bizjak <[email protected]>

This obviously clears up the warning and all my machines booted
(although I don't think any of them actually exercise this code path?):

Tested-by: Nathan Chancellor <[email protected]>

> ---
> arch/x86/kernel/callthunks.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c
> index f5507c95e7be..c561dd481eb9 100644
> --- a/arch/x86/kernel/callthunks.c
> +++ b/arch/x86/kernel/callthunks.c
> @@ -306,7 +306,7 @@ static bool is_callthunk(void *addr)
> if (!thunks_initialized || skip_addr((void *)dest))
> return false;
>
> - *pad = dest - tmpl_size;
> + pad = (void *)(dest - tmpl_size);
>
> memcpy(insn_buff, skl_call_thunk_template, tmpl_size);
> apply_relocation(insn_buff, tmpl_size, pad,
> --
> 2.31.1
>

2023-12-02 13:08:22

by tip-bot2 for Alexey Makhalov

Subject: [tip: x86/percpu] x86/callthunks: Correct calculation of dest address in is_callthunk()

The following commit has been merged into the x86/percpu branch of tip:

Commit-ID: fc50065325f8b88d6986f089ae103b5db858ab96
Gitweb: https://git.kernel.org/tip/fc50065325f8b88d6986f089ae103b5db858ab96
Author: Uros Bizjak <[email protected]>
AuthorDate: Fri, 01 Dec 2023 09:57:27 +01:00
Committer: Ingo Molnar <[email protected]>
CommitterDate: Sat, 02 Dec 2023 10:51:28 +01:00

x86/callthunks: Correct calculation of dest address in is_callthunk()

GCC didn't warn on the invalid use of relocation destination
pointer, so the calculated destination value was applied to
the uninitialized pointer location in error.

Fixes: 17bce3b2ae2d ("x86/callthunks: Handle %rip-relative relocations in call thunk template")
Reported-by: Nathan Chancellor <[email protected]>
Signed-off-by: Uros Bizjak <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Closes: https://lore.kernel.org/lkml/[email protected]/
Link: https://lore.kernel.org/r/[email protected]
---
arch/x86/kernel/callthunks.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c
index f56fa30..2324c7f 100644
--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -312,7 +312,7 @@ static bool is_callthunk(void *addr)
if (!thunks_initialized || skip_addr((void *)dest))
return false;

- *pad = dest - tmpl_size;
+ pad = (void *)(dest - tmpl_size);

memcpy(insn_buff, skl_call_thunk_template, tmpl_size);
apply_relocation(insn_buff, tmpl_size, pad,