linux-kernel - [PATCH 2/2] RISC-V: kexec: Fix memory leak of elf header buffer

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Date:   Fri, 4 Nov 2022 17:56:58 +0800
From:   Li Huafei <lihuafei1@...wei.com>
To:     <paul.walmsley@...ive.com>, <palmer@...belt.com>,
        <aou@...s.berkeley.edu>, <lizhengyu3@...wei.com>,
        <liaochang1@...wei.com>, <u.kleine-koenig@...gutronix.de>,
        <rdunlap@...radead.org>
CC:     <linux-riscv@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <kexec@...ts.infradead.org>, <lihuafei1@...wei.com>
Subject: [PATCH 2/2] RISC-V: kexec: Fix memory leak of elf header buffer

This is reported by kmemleak detector:

unreferenced object 0xff2000000403d000 (size 4096):
  comm "kexec", pid 146, jiffies 4294900633 (age 64.792s)
  hex dump (first 32 bytes):
    7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00  .ELF............
    04 00 f3 00 01 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<00000000566ca97c>] kmemleak_vmalloc+0x3c/0xbe
    [<00000000979283d8>] __vmalloc_node_range+0x3ac/0x560
    [<00000000b4b3712a>] __vmalloc_node+0x56/0x62
    [<00000000854f75e2>] vzalloc+0x2c/0x34
    [<00000000e9a00db9>] crash_prepare_elf64_headers+0x80/0x30c
    [<0000000067e8bf48>] elf_kexec_load+0x3e8/0x4ec
    [<0000000036548e09>] kexec_image_load_default+0x40/0x4c
    [<0000000079fbe1b4>] sys_kexec_file_load+0x1c4/0x322
    [<0000000040c62c03>] ret_from_syscall+0x0/0x2

In elf_kexec_load(), a buffer is allocated via vzalloc() to store elf
headers.  While it's not freed back to system when kdump kernel is
reloaded or unloaded, or when image->elf_header is successfully set and
then fails to load kdump kernel for some reason. Fix it by freeing the
buffer in arch_kimage_file_post_load_cleanup().

Fixes: 8acea455fafa ("RISC-V: Support for kexec_file on panic")
Signed-off-by: Li Huafei <lihuafei1@...wei.com>
---
 arch/riscv/kernel/elf_kexec.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
index ff30fcb43f47..5372b708fae2 100644
--- a/arch/riscv/kernel/elf_kexec.c
+++ b/arch/riscv/kernel/elf_kexec.c
@@ -26,6 +26,10 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 	kvfree(image->arch.fdt);
 	image->arch.fdt = NULL;
 
+	vfree(image->elf_headers);
+	image->elf_headers = NULL;
+	image->elf_headers_sz = 0;
+
 	return kexec_image_post_load_cleanup_default(image);
 }
 
-- 
2.17.1