[PATCH] x86/kexec: Fix double-free of elf header buffer

[PATCH] x86/kexec: Fix double-free of elf header buffer

[Takashi Iwai]

The recent fix for memory leaks forgot to clear the error path that
already does vfree() for the elf headers.  This may result in a
double-free.

Drop the superfluous vfree() call at the error path of
crash_load_segments().

Fixes: b3e34a47f989 ("x86/kexec: fix memory leak of elf header buffer")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 arch/x86/kernel/crash.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 9730c88530fc..305514431f26 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -401,10 +401,8 @@ int crash_load_segments(struct kimage *image)
 	kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
 	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
 	ret = kexec_add_buffer(&kbuf);
-	if (ret) {
-		vfree((void *)image->elf_headers);
+	if (ret)
 		return ret;
-	}
 	image->elf_load_addr = kbuf.mem;
 	pr_debug("Loaded ELF headers at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
 		 image->elf_load_addr, kbuf.bufsz, kbuf.memsz);
-- 
2.35.3

Re: [PATCH] x86/kexec: Fix double-free of elf header buffer

[Baoquan He]

CC kexec@lists.infradead.org

On 11/22/22 at 12:51pm, Takashi Iwai wrote:
> The recent fix for memory leaks forgot to clear the error path that
> already does vfree() for the elf headers.  This may result in a
> double-free.

Good catch. 

The log can be improved to make the issue more obvious. How about this:
======
With commit b3e34a47f989 ("x86/kexec: fix memory leak of elf header
buffer"), freeing up image->elf_headers in error path of
crash_load_segments() is not needed, because later
kimage_file_post_load_cleanup() will cover it. And not clearing it could 
result in a double-free.

Drop the superfluous vfree() call at the error path of
crash_load_segments().
========

Other than the log part, LGTM. Thanks.

Acked-by: Baoquan He <bhe@redhat.com>

> 
> Drop the superfluous vfree() call at the error path of
> crash_load_segments().
> 
> Fixes: b3e34a47f989 ("x86/kexec: fix memory leak of elf header buffer")
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ---
>  arch/x86/kernel/crash.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index 9730c88530fc..305514431f26 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -401,10 +401,8 @@ int crash_load_segments(struct kimage *image)
>  	kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
>  	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
>  	ret = kexec_add_buffer(&kbuf);
> -	if (ret) {
> -		vfree((void *)image->elf_headers);
> +	if (ret)
>  		return ret;
> -	}
>  	image->elf_load_addr = kbuf.mem;
>  	pr_debug("Loaded ELF headers at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
>  		 image->elf_load_addr, kbuf.bufsz, kbuf.memsz);
> -- 
> 2.35.3
> 

Re: [PATCH] x86/kexec: Fix double-free of elf header buffer

[Vlastimil Babka]

On 11/22/22 12:51, Takashi Iwai wrote:
> The recent fix for memory leaks forgot to clear the error path that
> already does vfree() for the elf headers.  This may result in a
> double-free.
> 
> Drop the superfluous vfree() call at the error path of
> crash_load_segments().
> 
> Fixes: b3e34a47f989 ("x86/kexec: fix memory leak of elf header buffer")
> Signed-off-by: Takashi Iwai <tiwai@suse.de>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  arch/x86/kernel/crash.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index 9730c88530fc..305514431f26 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -401,10 +401,8 @@ int crash_load_segments(struct kimage *image)
>  	kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
>  	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
>  	ret = kexec_add_buffer(&kbuf);
> -	if (ret) {
> -		vfree((void *)image->elf_headers);
> +	if (ret)
>  		return ret;
> -	}
>  	image->elf_load_addr = kbuf.mem;
>  	pr_debug("Loaded ELF headers at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
>  		 image->elf_load_addr, kbuf.bufsz, kbuf.memsz);

[tip: x86/urgent] x86/kexec: Fix double-free of elf header buffer

[tip-bot2 for Takashi Iwai]

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

Commit-ID:     d00dd2f2645dca04cf399d8fc692f3f69b6dd996
Gitweb:        https://git.kernel.org/tip/d00dd2f2645dca04cf399d8fc692f3f69b6dd996
Author:        Takashi Iwai <tiwai@suse.de>
AuthorDate:    Tue, 22 Nov 2022 12:51:22 +01:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Mon, 02 Jan 2023 18:56:21 +01:00

x86/kexec: Fix double-free of elf header buffer

After

  b3e34a47f989 ("x86/kexec: fix memory leak of elf header buffer"),

freeing image->elf_headers in the error path of crash_load_segments()
is not needed because kimage_file_post_load_cleanup() will take
care of that later. And not clearing it could result in a double-free.

Drop the superfluous vfree() call at the error path of
crash_load_segments().

Fixes: b3e34a47f989 ("x86/kexec: fix memory leak of elf header buffer")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/20221122115122.13937-1-tiwai@suse.de
---
 arch/x86/kernel/crash.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 9730c88..3055144 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -401,10 +401,8 @@ int crash_load_segments(struct kimage *image)
 	kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
 	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
 	ret = kexec_add_buffer(&kbuf);
-	if (ret) {
-		vfree((void *)image->elf_headers);
+	if (ret)
 		return ret;
-	}
 	image->elf_load_addr = kbuf.mem;
 	pr_debug("Loaded ELF headers at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
 		 image->elf_load_addr, kbuf.bufsz, kbuf.memsz);