[PATCH] powerpc/lib: fix book3s/32 boot failure due to code patching

[PATCH] powerpc/lib: fix book3s/32 boot failure due to code patching

[Christophe Leroy]

Commit 51c3c62b58b3 ("powerpc: Avoid code patching freed init
sections") accesses 'init_mem_is_free' flag too early, before the
kernel is relocated. This provokes early boot failure (before the
console is active).

As it is not necessary to do this verification that early, this
patch moves the test into patch_instruction() instead of
__patch_instruction().

This modification also has the advantage of avoiding unnecessary
remappings.

Fixes: 51c3c62b58b3 ("powerpc: Avoid code patching freed init sections")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/lib/code-patching.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 6ae2777c220d..5ffee298745f 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -28,12 +28,6 @@ static int __patch_instruction(unsigned int *exec_addr, unsigned int instr,
 {
 	int err;
 
-	/* Make sure we aren't patching a freed init section */
-	if (init_mem_is_free && init_section_contains(exec_addr, 4)) {
-		pr_debug("Skipping init section patching addr: 0x%px\n", exec_addr);
-		return 0;
-	}
-
 	__put_user_size(instr, patch_addr, 4, err);
 	if (err)
 		return err;
@@ -148,7 +142,7 @@ static inline int unmap_patch_area(unsigned long addr)
 	return 0;
 }
 
-int patch_instruction(unsigned int *addr, unsigned int instr)
+static int do_patch_instruction(unsigned int *addr, unsigned int instr)
 {
 	int err;
 	unsigned int *patch_addr = NULL;
@@ -188,12 +182,22 @@ int patch_instruction(unsigned int *addr, unsigned int instr)
 }
 #else /* !CONFIG_STRICT_KERNEL_RWX */
 
-int patch_instruction(unsigned int *addr, unsigned int instr)
+static int do_patch_instruction(unsigned int *addr, unsigned int instr)
 {
 	return raw_patch_instruction(addr, instr);
 }
 
 #endif /* CONFIG_STRICT_KERNEL_RWX */
+
+int patch_instruction(unsigned int *addr, unsigned int instr)
+{
+	/* Make sure we aren't patching a freed init section */
+	if (init_mem_is_free && init_section_contains(addr, 4)) {
+		pr_debug("Skipping init section patching addr: 0x%px\n", addr);
+		return 0;
+	}
+	return do_patch_instruction(addr, instr);
+}
 NOKPROBE_SYMBOL(patch_instruction);
 
 int patch_branch(unsigned int *addr, unsigned long target, int flags)
-- 
2.13.3

Re: [PATCH] powerpc/lib: fix book3s/32 boot failure due to code patching

[Michael Neuling]

On Mon, 2018-10-01 at 12:21 +0000, Christophe Leroy wrote:
> Commit 51c3c62b58b3 ("powerpc: Avoid code patching freed init
> sections") accesses 'init_mem_is_free' flag too early, before the
> kernel is relocated. This provokes early boot failure (before the
> console is active).
> 
> As it is not necessary to do this verification that early, this
> patch moves the test into patch_instruction() instead of
> __patch_instruction().
> 
> This modification also has the advantage of avoiding unnecessary
> remappings.
> 
> Fixes: 51c3c62b58b3 ("powerpc: Avoid code patching freed init sections")
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Thanks

Acked-by: Michael Neuling <mikey@neuling.org>

The original patch was also marked for stable so we should do the same here.

Cc: stable@vger.kernel.org # 4.13+

> ---
>  arch/powerpc/lib/code-patching.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-
> patching.c
> index 6ae2777c220d..5ffee298745f 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -28,12 +28,6 @@ static int __patch_instruction(unsigned int *exec_addr,
> unsigned int instr,
>  {
>  	int err;
>  
> -	/* Make sure we aren't patching a freed init section */
> -	if (init_mem_is_free && init_section_contains(exec_addr, 4)) {
> -		pr_debug("Skipping init section patching addr: 0x%px\n",
> exec_addr);
> -		return 0;
> -	}
> -
>  	__put_user_size(instr, patch_addr, 4, err);
>  	if (err)
>  		return err;
> @@ -148,7 +142,7 @@ static inline int unmap_patch_area(unsigned long addr)
>  	return 0;
>  }
>  
> -int patch_instruction(unsigned int *addr, unsigned int instr)
> +static int do_patch_instruction(unsigned int *addr, unsigned int instr)
>  {
>  	int err;
>  	unsigned int *patch_addr = NULL;
> @@ -188,12 +182,22 @@ int patch_instruction(unsigned int *addr, unsigned int
> instr)
>  }
>  #else /* !CONFIG_STRICT_KERNEL_RWX */
>  
> -int patch_instruction(unsigned int *addr, unsigned int instr)
> +static int do_patch_instruction(unsigned int *addr, unsigned int instr)
>  {
>  	return raw_patch_instruction(addr, instr);
>  }
>  
>  #endif /* CONFIG_STRICT_KERNEL_RWX */
> +
> +int patch_instruction(unsigned int *addr, unsigned int instr)
> +{
> +	/* Make sure we aren't patching a freed init section */
> +	if (init_mem_is_free && init_section_contains(addr, 4)) {
> +		pr_debug("Skipping init section patching addr: 0x%px\n", addr);
> +		return 0;
> +	}
> +	return do_patch_instruction(addr, instr);
> +}
>  NOKPROBE_SYMBOL(patch_instruction);
>  
>  int patch_branch(unsigned int *addr, unsigned long target, int flags)

Re: powerpc/lib: fix book3s/32 boot failure due to code patching

[Michael Ellerman]

On Mon, 2018-10-01 at 12:21:10 UTC, Christophe Leroy wrote:
> Commit 51c3c62b58b3 ("powerpc: Avoid code patching freed init
> sections") accesses 'init_mem_is_free' flag too early, before the
> kernel is relocated. This provokes early boot failure (before the
> console is active).
> 
> As it is not necessary to do this verification that early, this
> patch moves the test into patch_instruction() instead of
> __patch_instruction().
> 
> This modification also has the advantage of avoiding unnecessary
> remappings.
> 
> Fixes: 51c3c62b58b3 ("powerpc: Avoid code patching freed init sections")
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/b45ba4a51cde29b2939365ef0c07ad

cheers

Re: [PATCH] powerpc/lib: fix book3s/32 boot failure due to code patching

[Christophe Leroy]

Oops, forgot to tell it's for 4.9. Resending with proper subject.

Le 15/05/2019 à 08:39, Christophe Leroy a écrit :
> [Backport of upstream commit b45ba4a51cde29b2939365ef0c07ad34c8321789]
> 
> On powerpc32, patch_instruction() is called by apply_feature_fixups()
> which is called from early_init()
> 
> There is the following note in front of early_init():
>   * Note that the kernel may be running at an address which is different
>   * from the address that it was linked at, so we must use RELOC/PTRRELOC
>   * to access static data (including strings).  -- paulus
> 
> Therefore init_mem_is_free must be accessed with PTRRELOC()
> 
> Fixes: 1c38a84d4586 ("powerpc: Avoid code patching freed init sections")
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=203597
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> 
> ---
> Can't apply the upstream commit as such due to several other unrelated stuff
> like for instance STRICT_KERNEL_RWX which are missing.
> So instead, using same approach as for commit 252eb55816a6f69ef9464cad303cdb3326cdc61d
> ---
>   arch/powerpc/lib/code-patching.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
> index 14535ad4cdd1..c312955977ce 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -23,7 +23,7 @@ int patch_instruction(unsigned int *addr, unsigned int instr)
>   	int err;
>   
>   	/* Make sure we aren't patching a freed init section */
> -	if (init_mem_is_free && init_section_contains(addr, 4)) {
> +	if (*PTRRELOC(&init_mem_is_free) && init_section_contains(addr, 4)) {
>   		pr_debug("Skipping init section patching addr: 0x%px\n", addr);
>   		return 0;
>   	}
>