Re: [PATCH][v10] PM / hibernate: Verify the consistent of e820 memory map by md5 digest
Hi,
On Thu, Oct 13, 2016 at 03:10:18PM +0200, Denys Vlasenko wrote:
> On Fri, Sep 9, 2016 at 2:21 PM, Chen Yu wrote:
> > On some platforms, there is occasional panic triggered when trying to
> > resume from hibernation, a typical panic looks like:
> >
> > "BUG: unable to handle kernel paging request at 880085894000
> > IP: [] load_image_lzo+0x8c2/0xe70"
> >
> > Investigation carried out by Lee Chun-Yi show that this is because
> > e820 map has been changed by BIOS across hibernation, and one
> > of the page frames from suspend kernel is right located in restore
> > kernel's unmapped region, so panic comes out when accessing unmapped
> > kernel address.
> >
> > In order to expose this issue earlier, the md5 hash of e820 map
> > is passed from suspend kernel to restore kernel, and the restore
> > kernel will terminate the resume process once it finds the md5
> > hash are not the same.
> >
> > As the format of image header has been modified, the magic number
> > should also be adjusted as kernels with the same RESTORE_MAGIC have
> > to use the same header format and interpret all of the fields in
> > it in the same way.
> >
> > If the suspend kernel is built without md5 support, and the restore
> > kernel has md5 support, then the latter will bypass the check process.
> > Vice versa the restore kernel will bypass the check if it does not
> > support md5 operation.
> >
> > Note:
> > 1. Without this patch applied, it is possible that BIOS has
> >provided an inconsistent memory map, but the resume kernel is still
> >able to restore the image anyway(e.g, E820_RAM region is the superset
> >of the previous one), although the system might be unstable. So this
> >patch tries to treat any inconsistent e820 as illegal.
> >
> > 2. Another case is, this patch replies on comparing the e820_saved, but
> >currently the e820_save might not be strictly the same across
> >hibernation, even if BIOS has provided consistent e820 map - In
> >theory mptable might modify the BIOS-provided e820_saved dynamically
> >in early_reserve_e820_mpc_new, which would allocate a buffer from
> >E820_RAM, and marks it from E820_RAM to E820_RESERVED).
> >This is a potential and rare case we need to deal with in OS in
> >the future.
> >
> > Suggested-by: Pavel Machek
> > Suggested-by: Rafael J. Wysocki
> > Cc: Rafael J. Wysocki
> > Cc: Pavel Machek
> > Cc: Lee Chun-Yi
> > Cc: Borislav Petkov
> > Acked-by: Pavel Machek
> > Signed-off-by: Chen Yu
> > ---
>
> > +static int get_e820_md5(struct e820map *map, void *buf)
> > +{
> > + struct scatterlist sg;
> > + struct crypto_ahash *tfm;
> > + struct ahash_request *req;
> > + int ret = 0;
> > +
> > + tfm = crypto_alloc_ahash("md5", 0, CRYPTO_ALG_ASYNC);
> > + if (IS_ERR(tfm))
> > + return -ENOMEM;
> > +
> > + req = ahash_request_alloc(tfm, GFP_KERNEL);
> > + if (!req) {
> > + ret = -ENOMEM;
> > + goto free_ahash;
> > + }
>
> I looked elsewhere in kernel, and there is this idiom for placing
> struct ahash_request on stack. Instead of the ahash_request_alloc()
> and never-actually-tirggering-error handling, you can do:
>
> {
> AHASH_REQUEST_ON_STACK(req, tfm);
>
> > +
> > + sg_init_one(&sg, (u8 *)map, sizeof(struct e820map));
> > + ahash_request_set_callback(req, 0, NULL, NULL);
> > + ahash_request_set_crypt(req, &sg, buf, sizeof(struct e820map));
> > +
> > + if (crypto_ahash_digest(req))
> > + ret = -EINVAL;
> > +
> > + ahash_request_free(req);
> > + free_ahash:
>
> and, naturally, the free() and the label would not be needed too,
> just close the one extra brace:
>
> > + crypto_free_ahash(tfm);
> > +
> > + return ret;
>
> }
>
> > +}
OK, thanks for point it out, will do in next version.
Yu
Re: [PATCH][v10] PM / hibernate: Verify the consistent of e820 memory map by md5 digest
On Fri, Sep 9, 2016 at 2:21 PM, Chen Yu wrote:
> On some platforms, there is occasional panic triggered when trying to
> resume from hibernation, a typical panic looks like:
>
> "BUG: unable to handle kernel paging request at 880085894000
> IP: [] load_image_lzo+0x8c2/0xe70"
>
> Investigation carried out by Lee Chun-Yi show that this is because
> e820 map has been changed by BIOS across hibernation, and one
> of the page frames from suspend kernel is right located in restore
> kernel's unmapped region, so panic comes out when accessing unmapped
> kernel address.
>
> In order to expose this issue earlier, the md5 hash of e820 map
> is passed from suspend kernel to restore kernel, and the restore
> kernel will terminate the resume process once it finds the md5
> hash are not the same.
>
> As the format of image header has been modified, the magic number
> should also be adjusted as kernels with the same RESTORE_MAGIC have
> to use the same header format and interpret all of the fields in
> it in the same way.
>
> If the suspend kernel is built without md5 support, and the restore
> kernel has md5 support, then the latter will bypass the check process.
> Vice versa the restore kernel will bypass the check if it does not
> support md5 operation.
>
> Note:
> 1. Without this patch applied, it is possible that BIOS has
>provided an inconsistent memory map, but the resume kernel is still
>able to restore the image anyway(e.g, E820_RAM region is the superset
>of the previous one), although the system might be unstable. So this
>patch tries to treat any inconsistent e820 as illegal.
>
> 2. Another case is, this patch replies on comparing the e820_saved, but
>currently the e820_save might not be strictly the same across
>hibernation, even if BIOS has provided consistent e820 map - In
>theory mptable might modify the BIOS-provided e820_saved dynamically
>in early_reserve_e820_mpc_new, which would allocate a buffer from
>E820_RAM, and marks it from E820_RAM to E820_RESERVED).
>This is a potential and rare case we need to deal with in OS in
>the future.
>
> Suggested-by: Pavel Machek
> Suggested-by: Rafael J. Wysocki
> Cc: Rafael J. Wysocki
> Cc: Pavel Machek
> Cc: Lee Chun-Yi
> Cc: Borislav Petkov
> Acked-by: Pavel Machek
> Signed-off-by: Chen Yu
> ---
> +static int get_e820_md5(struct e820map *map, void *buf)
> +{
> + struct scatterlist sg;
> + struct crypto_ahash *tfm;
> + struct ahash_request *req;
> + int ret = 0;
> +
> + tfm = crypto_alloc_ahash("md5", 0, CRYPTO_ALG_ASYNC);
> + if (IS_ERR(tfm))
> + return -ENOMEM;
> +
> + req = ahash_request_alloc(tfm, GFP_KERNEL);
> + if (!req) {
> + ret = -ENOMEM;
> + goto free_ahash;
> + }
I looked elsewhere in kernel, and there is this idiom for placing
struct ahash_request on stack. Instead of the ahash_request_alloc()
and never-actually-tirggering-error handling, you can do:
{
AHASH_REQUEST_ON_STACK(req, tfm);
> +
> + sg_init_one(&sg, (u8 *)map, sizeof(struct e820map));
> + ahash_request_set_callback(req, 0, NULL, NULL);
> + ahash_request_set_crypt(req, &sg, buf, sizeof(struct e820map));
> +
> + if (crypto_ahash_digest(req))
> + ret = -EINVAL;
> +
> + ahash_request_free(req);
> + free_ahash:
and, naturally, the free() and the label would not be needed too,
just close the one extra brace:
> + crypto_free_ahash(tfm);
> +
> + return ret;
}
> +}
RE: [PATCH][v10] PM / hibernate: Verify the consistent of e820 memory map by md5 digest
Hi,
Sorry for late response, I missed the thread in mailbox,
> -Original Message-
> From: rjwyso...@gmail.com [mailto:rjwyso...@gmail.com] On Behalf Of
> Rafael J. Wysocki
> Sent: Monday, September 19, 2016 7:46 PM
> To: Chen, Yu C
> Cc: Linux PM; the arch/x86 maintainers; Linux Kernel Mailing List; Thomas
> Gleixner; Ingo Molnar; H. Peter Anvin; Wysocki, Rafael J; Pavel Machek; Lee
> Chun-Yi; Borislav Petkov
> Subject: Re: [PATCH][v10] PM / hibernate: Verify the consistent of e820
> memory map by md5 digest
>
> On Fri, Sep 9, 2016 at 2:21 PM, Chen Yu wrote:
> > On some platforms, there is occasional panic triggered when trying to
> > resume from hibernation, a typical panic looks like:
>
> [cut]
>
> > @@ -211,10 +292,15 @@ int arch_hibernation_header_save(void *addr,
> unsigned int max_size)
> > */
> > int arch_hibernation_header_restore(void *addr) {
> > + bool e820_mismatch = false;
>
> The extra local variable can be avoided if you structure the code slightly
> differently.
>
> > struct restore_data_record *rdr = addr;
> >
> > restore_jump_address = rdr->jump_address;
> > jump_address_phys = rdr->jump_address_phys;
> > restore_cr3 = rdr->cr3;
> > - return (rdr->magic == RESTORE_MAGIC) ? 0 : -EINVAL;
> > +
> > + e820_mismatch = hibernation_e820_mismatch(rdr->e820_digest);
>
> Also calling hibernation_e820_mismatch() before checking rdr->magic may not
> be useful at all.
>
Yes.
> > +
> > + return (rdr->magic == RESTORE_MAGIC) ?
> > + (e820_mismatch ? -ENODEV : 0) : -EINVAL;
>
> So what about:
>
> if (rdr->magic != RESTORE_MAGIC)
> return -EINVAL;
>
> if (hibernation_e820_mismatch(rdr->e820_digest))
> return -ENODEV;
>
> return 0;
>
>
Ok, will change it to this one. Thanks.
> > }
> > --
>
> Thanks,
> Rafael
Thanks,
Yu
RE: [PATCH][v10] PM / hibernate: Verify the consistent of e820 memory map by md5 digest
Hi,
Sorry for late response, I missed this thread in mailbox,
> -Original Message-
> From: rjwyso...@gmail.com [mailto:rjwyso...@gmail.com] On Behalf Of
> Rafael J. Wysocki
> Sent: Monday, September 19, 2016 7:46 PM
> To: Chen, Yu C
> Cc: Linux PM; the arch/x86 maintainers; Linux Kernel Mailing List; Thomas
> Gleixner; Ingo Molnar; H. Peter Anvin; Wysocki, Rafael J; Pavel Machek; Lee
> Chun-Yi; Borislav Petkov
> Subject: Re: [PATCH][v10] PM / hibernate: Verify the consistent of e820
> memory map by md5 digest
>
> On Fri, Sep 9, 2016 at 2:21 PM, Chen Yu wrote:
> > On some platforms, there is occasional panic triggered when trying to
> > resume from hibernation, a typical panic looks like:
>
> [cut]
>
> > @@ -211,10 +292,15 @@ int arch_hibernation_header_save(void *addr,
> unsigned int max_size)
> > */
> > int arch_hibernation_header_restore(void *addr) {
> > + bool e820_mismatch = false;
>
> The extra local variable can be avoided if you structure the code slightly
> differently.
>
> > struct restore_data_record *rdr = addr;
> >
> > restore_jump_address = rdr->jump_address;
> > jump_address_phys = rdr->jump_address_phys;
> > restore_cr3 = rdr->cr3;
> > - return (rdr->magic == RESTORE_MAGIC) ? 0 : -EINVAL;
> > +
> > + e820_mismatch = hibernation_e820_mismatch(rdr->e820_digest);
>
> Also calling hibernation_e820_mismatch() before checking rdr->magic may not
> be useful at all.
Yes.
>
> > +
> > + return (rdr->magic == RESTORE_MAGIC) ?
> > + (e820_mismatch ? -ENODEV : 0) : -EINVAL;
>
> So what about:
>
> if (rdr->magic != RESTORE_MAGIC)
> return -EINVAL;
>
> if (hibernation_e820_mismatch(rdr->e820_digest))
> return -ENODEV;
>
> return 0;
>
OK, will change it to this one. Thanks!
> > }
> > --
>
> Thanks,
> Rafael
Thanks,
Yu
Re: [PATCH][v10] PM / hibernate: Verify the consistent of e820 memory map by md5 digest
On Fri, Sep 9, 2016 at 2:21 PM, Chen Yu wrote:
> On some platforms, there is occasional panic triggered when trying to
> resume from hibernation, a typical panic looks like:
[cut]
> @@ -211,10 +292,15 @@ int arch_hibernation_header_save(void *addr, unsigned
> int max_size)
> */
> int arch_hibernation_header_restore(void *addr)
> {
> + bool e820_mismatch = false;
The extra local variable can be avoided if you structure the code
slightly differently.
> struct restore_data_record *rdr = addr;
>
> restore_jump_address = rdr->jump_address;
> jump_address_phys = rdr->jump_address_phys;
> restore_cr3 = rdr->cr3;
> - return (rdr->magic == RESTORE_MAGIC) ? 0 : -EINVAL;
> +
> + e820_mismatch = hibernation_e820_mismatch(rdr->e820_digest);
Also calling hibernation_e820_mismatch() before checking rdr->magic
may not be useful at all.
> +
> + return (rdr->magic == RESTORE_MAGIC) ?
> + (e820_mismatch ? -ENODEV : 0) : -EINVAL;
So what about:
if (rdr->magic != RESTORE_MAGIC)
return -EINVAL;
if (hibernation_e820_mismatch(rdr->e820_digest))
return -ENODEV;
return 0;
> }
> --
Thanks,
Rafael
