RISC-V: kexec: Fix memory leak of fdt buffer

commit 96df59b1ae23f5c11698c3c2159aeb2ecd4944a4 upstream.

This is reported by kmemleak detector:

unreferenced object 0xff60000082864000 (size 9588):
  comm "kexec", pid 146, jiffies 4294900634 (age 64.788s)
  hex dump (first 32 bytes):
    d0 0d fe ed 00 00 12 ed 00 00 00 48 00 00 11 40  ...........H...@
    00 00 00 28 00 00 00 11 00 00 00 02 00 00 00 00  ...(............
  backtrace:
    [<00000000f95b17c4>] kmemleak_alloc+0x34/0x3e
    [<00000000b9ec8e3e>] kmalloc_order+0x9c/0xc4
    [<00000000a95cf02e>] kmalloc_order_trace+0x34/0xb6
    [<00000000f01e68b4>] __kmalloc+0x5c2/0x62a
    [<000000002bd497b2>] kvmalloc_node+0x66/0xd6
    [<00000000906542fa>] of_kexec_alloc_and_setup_fdt+0xa6/0x6ea
    [<00000000e1166bde>] elf_kexec_load+0x206/0x4ec
    [<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 kvmalloc() to store fdt.
While it's not freed back to system when kexec kernel is reloaded or
unloaded.  Then memory leak is caused.  Fix it by introducing riscv
specific function arch_kimage_file_post_load_cleanup(), and freeing the
buffer there.

Fixes: 6261586e0c91 ("RISC-V: Add kexec_file support")
Signed-off-by: Li Huafei <lihuafei1@huawei.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Liao Chang <liaochang1@huawei.com>
Link: https://lore.kernel.org/r/20221104095658.141222-1-lihuafei1@huawei.com
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
index 0cb94992c15b..ff30fcb43f47 100644
--- a/arch/riscv/kernel/elf_kexec.c
+++ b/arch/riscv/kernel/elf_kexec.c
@@ -21,6 +21,14 @@
 #include <linux/memblock.h>
 #include <asm/setup.h>
 
+int arch_kimage_file_post_load_cleanup(struct kimage *image)
+{
+	kvfree(image->arch.fdt);
+	image->arch.fdt = NULL;
+
+	return kexec_image_post_load_cleanup_default(image);
+}
+
 static int riscv_kexec_elf_load(struct kimage *image, struct elfhdr *ehdr,
 				struct kexec_elf_info *elf_info, unsigned long old_pbase,
 				unsigned long new_pbase)
@@ -298,6 +306,8 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
 		pr_err("Error add DTB kbuf ret=%d\n", ret);
 		goto out_free_fdt;
 	}
+	/* Cache the fdt buffer address for memory cleanup */
+	image->arch.fdt = fdt;
 	pr_notice("Loaded device tree at 0x%lx\n", kbuf.mem);
 	goto out;