2022-11-22 12:44:59

by Takashi Iwai

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

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 <[email protected]>
---
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

2022-11-23 10:28:18

by Baoquan He

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

CC [email protected]

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 <[email protected]>

>
> 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 <[email protected]>
> ---
> 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
>

2023-01-02 11:49:53

by Vlastimil Babka

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

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 <[email protected]>

Acked-by: Vlastimil Babka <[email protected]>

> ---
> 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);

2023-01-02 18:20:25

by tip-bot2 for Alexey Makhalov

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

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 <[email protected]>
AuthorDate: Tue, 22 Nov 2022 12:51:22 +01:00
Committer: Borislav Petkov (AMD) <[email protected]>
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 <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Acked-by: Baoquan He <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
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);