Re: [PATCH 1/2] powerpc: Free fdt on error in elf64_load()

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On 4/20/21 10:35 PM, Santosh Sivaraj wrote:
Hi Santosh,


There are a few "goto out;" statements before the local variable "fdt"
is initialized through the call to of_kexec_alloc_and_setup_fdt() in
elf64_load().  This will result in an uninitialized "fdt" being passed
to kvfree() in this function if there is an error before the call to
of_kexec_alloc_and_setup_fdt().

If there is any error after fdt is allocated, but before it is
saved in the arch specific kimage struct, free the fdt.

Signed-off-by: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Suggested-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
---
  arch/powerpc/kexec/elf_64.c | 16 ++++++----------
  1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
index 5a569bb51349..02662e72c53d 100644
--- a/arch/powerpc/kexec/elf_64.c
+++ b/arch/powerpc/kexec/elf_64.c
@@ -114,7 +114,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
  	ret = setup_new_fdt_ppc64(image, fdt, initrd_load_addr,
  				  initrd_len, cmdline);
  	if (ret)
-		goto out;
+		goto out_free_fdt;

Shouldn't there be a goto out_free_fdt if fdt_open_into fails?

You are likely looking at elf_64.c in the mainline branch. The patch I have submitted is based on Rob's device-tree for-next branch. Please see the link below:

https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git/tree/arch/powerpc/kexec/elf_64.c?h=for-next


fdt_pack(fdt); @@ -125,7 +125,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
  	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
  	ret = kexec_add_buffer(&kbuf);
  	if (ret)
-		goto out;
+		goto out_free_fdt;
/* FDT will be freed in arch_kimage_file_post_load_cleanup */
  	image->arch.fdt = fdt;
@@ -140,18 +140,14 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
  	if (ret)
  		pr_err("Error setting up the purgatory.\n");
+ goto out;
+
+out_free_fdt:
+	kvfree(fdt);

Can just use kfree here?
"fdt" is allocated through kvmalloc(). So it is freed using kvfree.

thanks,
 -lakshmi

  out:
  	kfree(modified_cmdline);
  	kexec_free_elf_info(&elf_info);
- /*
-	 * Once FDT buffer has been successfully passed to kexec_add_buffer(),
-	 * the FDT buffer address is saved in image->arch.fdt. In that case,
-	 * the memory cannot be freed here in case of any other error.
-	 */
-	if (ret && !image->arch.fdt)
-		kvfree(fdt);
-
  	return ret ? ERR_PTR(ret) : NULL;
  }
--
2.31.0




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