Patchwork [01/11] x86/efi: Allocate e820 buffer before calling efi_exit_boot_service

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Submitter Ard Biesheuvel
Date Nov. 29, 2018, 5:12 p.m.
Message ID <20181129171230.18699-2-ard.biesheuvel@linaro.org>
Download mbox | patch
Permalink /patch/668371/
State New
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Comments

Ard Biesheuvel - Nov. 29, 2018, 5:12 p.m.
From: Eric Snowberg <eric.snowberg@oracle.com>

Commit d64934019f6c ("x86/efi: Use efi_exit_boot_services()")
introduced a regression on systems with large memory maps
causing them to hang on boot. The first "goto get_map" that was removed
from exit_boot insured there was enough room for the memory map when
efi_call_early(exit_boot_services) was called. This happens when
(nr_desc > ARRAY_SIZE(params->e820_table).

Chain of events:
  exit_boot()
    efi_exit_boot_services()
      efi_get_memory_map <- at this point the mm can't grow over 8 desc
      priv_func()
        exit_boot_func()
          allocate_e820ext() <- new mm grows over 8 desc from e820 alloc
      efi_call_early(exit_boot_services) <- mm key doesn't match so retry
      efi_call_early(get_memory_map) <- not enough room for new mm
      system hangs

This patch allocates the e820 buffer before calling efi_exit_boot_services
and fixes the regression.

Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 arch/x86/boot/compressed/eboot.c | 65 ++++++++++++++++++++------------
 1 file changed, 41 insertions(+), 24 deletions(-)
Ingo Molnar - Nov. 30, 2018, 7:29 a.m.
* Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:

> From: Eric Snowberg <eric.snowberg@oracle.com>
> 
> Commit d64934019f6c ("x86/efi: Use efi_exit_boot_services()")
> introduced a regression on systems with large memory maps
> causing them to hang on boot. The first "goto get_map" that was removed
> from exit_boot insured there was enough room for the memory map when
> efi_call_early(exit_boot_services) was called. This happens when
> (nr_desc > ARRAY_SIZE(params->e820_table).
> 
> Chain of events:
>   exit_boot()
>     efi_exit_boot_services()
>       efi_get_memory_map <- at this point the mm can't grow over 8 desc
>       priv_func()
>         exit_boot_func()
>           allocate_e820ext() <- new mm grows over 8 desc from e820 alloc
>       efi_call_early(exit_boot_services) <- mm key doesn't match so retry
>       efi_call_early(get_memory_map) <- not enough room for new mm
>       system hangs
> 
> This patch allocates the e820 buffer before calling efi_exit_boot_services
> and fixes the regression.
> 
> Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  arch/x86/boot/compressed/eboot.c | 65 ++++++++++++++++++++------------
>  1 file changed, 41 insertions(+), 24 deletions(-)

Any objections against marking this for -stable and filing it in 
efi/urgent? Boot hangs are show-stopper bugs, so distributions would want 
to backport this fix anyway.

> +	boot_map.map =		&map;
> +	boot_map.map_size =	&map_size;
> +	boot_map.desc_size =	&desc_size;
> +	boot_map.desc_ver =	NULL;
> +	boot_map.key_ptr =	NULL;
> +	boot_map.buff_size =	&buff_size;

I have changed this to the canonical style, which is also used elsewhere 
in the file:

>  	map.buff_size		= &buff_size;
>  	priv.boot_params	= boot_params;
>  	priv.efi		= &boot_params->efi_info;
> -	priv.e820ext		= NULL;
> -	priv.e820ext_size	= 0;

I.e.:

+	boot_map.map		= &map;
+	boot_map.map_size	= &map_size;
+	boot_map.desc_size	= &desc_size;
+	boot_map.desc_ver	= NULL;
+	boot_map.key_ptr	= NULL;
+	boot_map.buff_size	= &buff_size;
+
+	status = efi_get_memory_map(sys_table, &boot_map);

Thanks,

	Ingo
Ard Biesheuvel - Nov. 30, 2018, 8:26 a.m.
On Fri, 30 Nov 2018 at 08:29, Ingo Molnar <mingo@kernel.org> wrote:
>
>
> * Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>
> > From: Eric Snowberg <eric.snowberg@oracle.com>
> >
> > Commit d64934019f6c ("x86/efi: Use efi_exit_boot_services()")
> > introduced a regression on systems with large memory maps
> > causing them to hang on boot. The first "goto get_map" that was removed
> > from exit_boot insured there was enough room for the memory map when
> > efi_call_early(exit_boot_services) was called. This happens when
> > (nr_desc > ARRAY_SIZE(params->e820_table).
> >
> > Chain of events:
> >   exit_boot()
> >     efi_exit_boot_services()
> >       efi_get_memory_map <- at this point the mm can't grow over 8 desc
> >       priv_func()
> >         exit_boot_func()
> >           allocate_e820ext() <- new mm grows over 8 desc from e820 alloc
> >       efi_call_early(exit_boot_services) <- mm key doesn't match so retry
> >       efi_call_early(get_memory_map) <- not enough room for new mm
> >       system hangs
> >
> > This patch allocates the e820 buffer before calling efi_exit_boot_services
> > and fixes the regression.
> >
> > Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > ---
> >  arch/x86/boot/compressed/eboot.c | 65 ++++++++++++++++++++------------
> >  1 file changed, 41 insertions(+), 24 deletions(-)
>
> Any objections against marking this for -stable and filing it in
> efi/urgent? Boot hangs are show-stopper bugs, so distributions would want
> to backport this fix anyway.
>

No objections per se, but this is the kind of patch that might go the
other way as well, so I would prefer to give it some wider coverage at
first, given how quickly patches are taken into -stable.

I can make a note of it and send it to Greg halfway into the next -rc cycle.

> > +     boot_map.map =          &map;
> > +     boot_map.map_size =     &map_size;
> > +     boot_map.desc_size =    &desc_size;
> > +     boot_map.desc_ver =     NULL;
> > +     boot_map.key_ptr =      NULL;
> > +     boot_map.buff_size =    &buff_size;
>
> I have changed this to the canonical style, which is also used elsewhere
> in the file:
>
> >       map.buff_size           = &buff_size;
> >       priv.boot_params        = boot_params;
> >       priv.efi                = &boot_params->efi_info;
> > -     priv.e820ext            = NULL;
> > -     priv.e820ext_size       = 0;
>
> I.e.:
>
> +       boot_map.map            = &map;
> +       boot_map.map_size       = &map_size;
> +       boot_map.desc_size      = &desc_size;
> +       boot_map.desc_ver       = NULL;
> +       boot_map.key_ptr        = NULL;
> +       boot_map.buff_size      = &buff_size;
> +
> +       status = efi_get_memory_map(sys_table, &boot_map);
>

Excellent, thanks.
Ingo Molnar - Nov. 30, 2018, 8:36 a.m.
* Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:

> On Fri, 30 Nov 2018 at 08:29, Ingo Molnar <mingo@kernel.org> wrote:
> >
> >
> > * Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> >
> > > From: Eric Snowberg <eric.snowberg@oracle.com>
> > >
> > > Commit d64934019f6c ("x86/efi: Use efi_exit_boot_services()")
> > > introduced a regression on systems with large memory maps
> > > causing them to hang on boot. The first "goto get_map" that was removed
> > > from exit_boot insured there was enough room for the memory map when
> > > efi_call_early(exit_boot_services) was called. This happens when
> > > (nr_desc > ARRAY_SIZE(params->e820_table).
> > >
> > > Chain of events:
> > >   exit_boot()
> > >     efi_exit_boot_services()
> > >       efi_get_memory_map <- at this point the mm can't grow over 8 desc
> > >       priv_func()
> > >         exit_boot_func()
> > >           allocate_e820ext() <- new mm grows over 8 desc from e820 alloc
> > >       efi_call_early(exit_boot_services) <- mm key doesn't match so retry
> > >       efi_call_early(get_memory_map) <- not enough room for new mm
> > >       system hangs
> > >
> > > This patch allocates the e820 buffer before calling efi_exit_boot_services
> > > and fixes the regression.
> > >
> > > Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
> > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > > ---
> > >  arch/x86/boot/compressed/eboot.c | 65 ++++++++++++++++++++------------
> > >  1 file changed, 41 insertions(+), 24 deletions(-)
> >
> > Any objections against marking this for -stable and filing it in
> > efi/urgent? Boot hangs are show-stopper bugs, so distributions would want
> > to backport this fix anyway.
> >
> 
> No objections per se, but this is the kind of patch that might go the
> other way as well, so I would prefer to give it some wider coverage at
> first, given how quickly patches are taken into -stable.
> 
> I can make a note of it and send it to Greg halfway into the next -rc cycle.

So there should be at least one week of testing because I just sent the 
EFI fixes to Linus, plus -stable gets at least a week of testing as well.

Also, in practice, -next and early -rc cycles get only the fraction of 
testing that later -rc's or -stable gets. So if we want this in -stable 
we might as well do it now - or the real testing gets delayed by ~3 
months in practice. That's also the pattern encouraged by Linus: if it's 
a fix that matters then it should be upstreamed with the usual regression 
fixes.

Anyway, your call!

Thanks,

	Ingo

Patch

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 8b4c5e001157..f7bad07bb251 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -1,3 +1,4 @@ 
+
 /* -----------------------------------------------------------------------
  *
  *   Copyright 2011 Intel Corporation; author Matt Fleming
@@ -634,37 +635,54 @@  static efi_status_t alloc_e820ext(u32 nr_desc, struct setup_data **e820ext,
 	return status;
 }
 
+static efi_status_t allocate_e820(struct boot_params *params,
+				  struct setup_data **e820ext,
+				  u32 *e820ext_size)
+{
+	unsigned long map_size, desc_size, buff_size;
+	struct efi_boot_memmap boot_map;
+	efi_memory_desc_t *map;
+	efi_status_t status;
+	__u32 nr_desc;
+
+	boot_map.map =		&map;
+	boot_map.map_size =	&map_size;
+	boot_map.desc_size =	&desc_size;
+	boot_map.desc_ver =	NULL;
+	boot_map.key_ptr =	NULL;
+	boot_map.buff_size =	&buff_size;
+
+	status = efi_get_memory_map(sys_table, &boot_map);
+	if (status != EFI_SUCCESS)
+		return status;
+
+	nr_desc = buff_size / desc_size;
+
+	if (nr_desc > ARRAY_SIZE(params->e820_table)) {
+		u32 nr_e820ext = nr_desc - ARRAY_SIZE(params->e820_table);
+
+		status = alloc_e820ext(nr_e820ext, e820ext, e820ext_size);
+		if (status != EFI_SUCCESS)
+			return status;
+	}
+
+	return EFI_SUCCESS;
+}
+
 struct exit_boot_struct {
 	struct boot_params	*boot_params;
 	struct efi_info		*efi;
-	struct setup_data	*e820ext;
-	__u32			e820ext_size;
 };
 
 static efi_status_t exit_boot_func(efi_system_table_t *sys_table_arg,
 				   struct efi_boot_memmap *map,
 				   void *priv)
 {
-	static bool first = true;
 	const char *signature;
 	__u32 nr_desc;
 	efi_status_t status;
 	struct exit_boot_struct *p = priv;
 
-	if (first) {
-		nr_desc = *map->buff_size / *map->desc_size;
-		if (nr_desc > ARRAY_SIZE(p->boot_params->e820_table)) {
-			u32 nr_e820ext = nr_desc -
-					ARRAY_SIZE(p->boot_params->e820_table);
-
-			status = alloc_e820ext(nr_e820ext, &p->e820ext,
-					       &p->e820ext_size);
-			if (status != EFI_SUCCESS)
-				return status;
-		}
-		first = false;
-	}
-
 	signature = efi_is_64bit() ? EFI64_LOADER_SIGNATURE
 				   : EFI32_LOADER_SIGNATURE;
 	memcpy(&p->efi->efi_loader_signature, signature, sizeof(__u32));
@@ -687,8 +705,8 @@  static efi_status_t exit_boot(struct boot_params *boot_params, void *handle)
 {
 	unsigned long map_sz, key, desc_size, buff_size;
 	efi_memory_desc_t *mem_map;
-	struct setup_data *e820ext;
-	__u32 e820ext_size;
+	struct setup_data *e820ext = NULL;
+	__u32 e820ext_size = 0;
 	efi_status_t status;
 	__u32 desc_version;
 	struct efi_boot_memmap map;
@@ -702,8 +720,10 @@  static efi_status_t exit_boot(struct boot_params *boot_params, void *handle)
 	map.buff_size		= &buff_size;
 	priv.boot_params	= boot_params;
 	priv.efi		= &boot_params->efi_info;
-	priv.e820ext		= NULL;
-	priv.e820ext_size	= 0;
+
+	status = allocate_e820(boot_params, &e820ext, &e820ext_size);
+	if (status != EFI_SUCCESS)
+		return status;
 
 	/* Might as well exit boot services now */
 	status = efi_exit_boot_services(sys_table, handle, &map, &priv,
@@ -711,9 +731,6 @@  static efi_status_t exit_boot(struct boot_params *boot_params, void *handle)
 	if (status != EFI_SUCCESS)
 		return status;
 
-	e820ext			= priv.e820ext;
-	e820ext_size		= priv.e820ext_size;
-
 	/* Historic? */
 	boot_params->alt_mem_k	= 32 * 1024;