On Tue, Apr 20, 2021 at 10:04 AM Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx> wrote: > > On 4/20/21 7:42 AM, Lakshmi Ramasubramanian wrote: > > On 4/20/21 6:06 AM, Rob Herring wrote: > >> On Tue, Apr 20, 2021 at 12:20 AM Lakshmi Ramasubramanian > >> <nramas@xxxxxxxxxxxxxxxxxxx> wrote: > >>> > >>> On 4/19/21 10:00 PM, Dan Carpenter wrote: > >>>> On Tue, Apr 20, 2021 at 09:30:16AM +1000, Michael Ellerman wrote: > >>>>> Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx> writes: > >>>>>> On 4/16/21 2:05 AM, Michael Ellerman wrote: > >>>>>> > >>>>>>> Daniel Axtens <dja@xxxxxxxxxx> writes: > >>>>>>>>> On 4/15/21 12:14 PM, Lakshmi Ramasubramanian wrote: > >>>>>>>>> > >>>>>>>>> Sorry - missed copying device-tree and powerpc mailing lists. > >>>>>>>>> > >>>>>>>>>> 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(). > >>>>>>>>>> > >>>>>>>>>> Initialize the local variable "fdt" to NULL. > >>>>>>>>>> > >>>>>>>> I'm a huge fan of initialising local variables! But I'm > >>>>>>>> struggling to > >>>>>>>> find the code path that will lead to an uninit fdt being > >>>>>>>> returned... > >>>>>>>> > >>>>>>>> The out label reads in part: > >>>>>>>> > >>>>>>>> /* Make kimage_file_post_load_cleanup free the fdt buffer for > >>>>>>>> us. */ > >>>>>>>> return ret ? ERR_PTR(ret) : fdt; > >>>>>>>> > >>>>>>>> As far as I can tell, any time we get a non-zero ret, we're > >>>>>>>> going to > >>>>>>>> return an error pointer rather than the uninitialised value... > >>>>>> > >>>>>> As Dan pointed out, the new code is in linux-next. > >>>>>> > >>>>>> I have copied the new one below - the function doesn't return fdt, > >>>>>> but > >>>>>> instead sets it in the arch specific field (please see the link to > >>>>>> the > >>>>>> updated elf_64.c below). > >>>>>> > >>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git/tree/arch/powerpc/kexec/elf_64.c?h=for-next > >>>>>> > >>>>>> > >>>>>>>> > >>>>>>>> (btw, it does look like we might leak fdt if we have an error > >>>>>>>> after we > >>>>>>>> successfully kmalloc it.) > >>>>>>>> > >>>>>>>> Am I missing something? Can you link to the report for the > >>>>>>>> kernel test > >>>>>>>> robot or from Dan? > >>>>>> > >>>>>> /* > >>>>>> * 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; > >>>>>> > >>>>>> In case of an error, the memory allocated for fdt is freed unless > >>>>>> it has > >>>>>> already been passed to kexec_add_buffer(). > >>>>> > >>>>> It feels like the root of the problem is that the kvfree of fdt is in > >>>>> the wrong place. It's only allocated later in the function, so the > >>>>> error > >>>>> path should reflect that. Something like the patch below. > >>>>> > >>>>> cheers > >>>>> > >>>>> > >>>>> 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; > >>>>> > >>>>> 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; > >>>> > >>>> This will leak. It would need to be something like: > >>>> > >>>> if (ret) { > >>>> pr_err("Error setting up the purgatory.\n"); > >>>> goto out_free_fdt; > >>>> } > >>> Once "fdt" buffer is successfully passed to kexec_add_buffer() it cannot > >>> be freed here - it will be freed when the kexec cleanup function is > >>> called. > >> > >> That may be the case currently, but really if a function returns an > >> error it should have undone anything it did like memory allocations. I > >> don't think you should do that to fix this issue, but it would be a > >> good clean-up. > >> > > > > I agree - in case of an error the function should do a proper clean-up. > > Just to be clear - for now, I will leave this as is. Correct? Yes. > > In my patch, I will do the following changes: > > > > => Free "fdt" when possible (as Michael had suggested in his patch) > > => Zero out "elf_info" struct at the start of the function. > > > > Instead of zeroing out "elf_info", I think it would be better to return > an error immediately, instead of the "goto out;", if > kexec_build_elf_info() fails. > > ret = kexec_build_elf_info(kernel_buf, kernel_len, &ehdr, &elf_info); > if (ret) > return ERR_PTR(ret); I thought kexec_build_elf_info() can return an error and allocated memory, so that would leak memory. Rob
