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Groups > linux.kernel > #1624673 > unrolled thread
| Started by | Baoquan He <bhe@redhat.com> |
|---|---|
| First post | 2017-04-17 15:40 +0200 |
| Last post | 2017-04-19 03:00 +0200 |
| Articles | 5 — 2 participants |
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[PATCH 3/4] KASLR: Handle memory limit specified by memmap and mem option Baoquan He <bhe@redhat.com> - 2017-04-17 15:40 +0200
Re: [PATCH 3/4] KASLR: Handle memory limit specified by memmap and mem option Kees Cook <keescook@chromium.org> - 2017-04-18 22:40 +0200
Re: [PATCH 3/4] KASLR: Handle memory limit specified by memmap and mem option Baoquan He <bhe@redhat.com> - 2017-04-19 01:20 +0200
Re: [PATCH 3/4] KASLR: Handle memory limit specified by memmap and mem option Baoquan He <bhe@redhat.com> - 2017-04-19 03:00 +0200
Re: [PATCH 3/4] KASLR: Handle memory limit specified by memmap and mem option Baoquan He <bhe@redhat.com> - 2017-04-19 03:00 +0200
| From | Baoquan He <bhe@redhat.com> |
|---|---|
| Date | 2017-04-17 15:40 +0200 |
| Subject | [PATCH 3/4] KASLR: Handle memory limit specified by memmap and mem option |
| Message-ID | <txf2N-1br-19@gated-at.bofh.it> |
Option mem= will limit the max address system can use. Any memory
region above the limit will be removed. And memmap=nn[KMG] which
has no offset specified has the same behaviour as mem=. KASLR need
consider this when choose the random position for decompressing
kernel. Do it in this patch.
Signed-off-by: Baoquan He <bhe@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: x86@kernel.org
Cc: Kees Cook <keescook@chromium.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
---
arch/x86/boot/compressed/kaslr.c | 53 +++++++++++++++++++++++++++++++---------
1 file changed, 42 insertions(+), 11 deletions(-)
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 36ab429..5361abd 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -67,6 +67,10 @@ int mem_avoid_memmap_index;
extern unsigned long get_cmd_line_ptr(void);
+/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
+unsigned long long mem_limit = ULLONG_MAX;
+
+
enum mem_avoid_index {
MEM_AVOID_ZO_RANGE = 0,
MEM_AVOID_INITRD,
@@ -117,15 +121,18 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
return -EINVAL;
switch (*p) {
- case '@':
- /* Skip this region, usable */
- *size = 0;
- *start = 0;
case '#':
case '$':
case '!':
*start = memparse(p + 1, &p);
return 0;
+ case '@':
+ /* Skip this region, usable */
+ *size = 0;
+ default:
+ /* Avoid the region which is above the amount limit */
+ *start = 0;
+ return 0;
}
return -EINVAL;
@@ -151,9 +158,14 @@ static void mem_avoid_memmap(char *str)
if (rc < 0)
break;
str = k;
- /* A usable region that should not be skipped */
- if (size == 0)
+
+ if (start == 0) {
+ /* Store the specified memory limit if size > 0 */
+ if (size > 0)
+ mem_limit = size;
+
continue;
+ }
mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start;
mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
@@ -173,6 +185,7 @@ static int handle_mem_memmap(void)
char tmp_cmdline[COMMAND_LINE_SIZE];
size_t len = strlen((char *)args);
char *param, *val;
+ u64 mem_size;
len = (len >= COMMAND_LINE_SIZE) ? COMMAND_LINE_SIZE - 1 : len;
memcpy(tmp_cmdline, args, len);
@@ -195,8 +208,18 @@ static int handle_mem_memmap(void)
return -1;
}
- if (!strcmp(param, "memmap"))
+ if (!strcmp(param, "memmap")) {
mem_avoid_memmap(val);
+ } else if (!strcmp(param, "mem")) {
+ char *p = val;
+
+ if (!strcmp(p, "nopentium"))
+ continue;
+ mem_size = memparse(p, &p);
+ if (mem_size == 0)
+ return -EINVAL;
+ mem_limit = mem_size;
+ }
}
return 0;
@@ -432,7 +455,8 @@ static void process_e820_entry(struct e820entry *entry,
{
struct mem_vector region, overlap;
struct slot_area slot_area;
- unsigned long start_orig;
+ unsigned long start_orig, end;
+ struct e820entry cur_entry;
/* Skip non-RAM entries. */
if (entry->type != E820_RAM)
@@ -446,8 +470,15 @@ static void process_e820_entry(struct e820entry *entry,
if (entry->addr + entry->size < minimum)
return;
- region.start = entry->addr;
- region.size = entry->size;
+ /* Ignore entries above memory limit */
+ end = min(entry->size + entry->addr - 1, mem_limit);
+ if (entry->addr >= end)
+ return;
+ cur_entry.addr = entry->addr;
+ cur_entry.size = end - entry->addr + 1;
+
+ region.start = cur_entry.addr;
+ region.size = cur_entry.size;
/* Give up if slot area array is full. */
while (slot_area_index < MAX_SLOT_AREA) {
@@ -461,7 +492,7 @@ static void process_e820_entry(struct e820entry *entry,
region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
/* Did we raise the address above this e820 region? */
- if (region.start > entry->addr + entry->size)
+ if (region.start > cur_entry.addr + cur_entry.size)
return;
/* Reduce size by any delta from the original address. */
--
2.5.5
[toc] | [next] | [standalone]
| From | Kees Cook <keescook@chromium.org> |
|---|---|
| Date | 2017-04-18 22:40 +0200 |
| Subject | Re: [PATCH 3/4] KASLR: Handle memory limit specified by memmap and mem option |
| Message-ID | <txI4N-2c8-1@gated-at.bofh.it> |
| In reply to | #1624673 |
On Mon, Apr 17, 2017 at 6:34 AM, Baoquan He <bhe@redhat.com> wrote:
> Option mem= will limit the max address system can use. Any memory
> region above the limit will be removed. And memmap=nn[KMG] which
> has no offset specified has the same behaviour as mem=. KASLR need
> consider this when choose the random position for decompressing
> kernel. Do it in this patch.
>
> Signed-off-by: Baoquan He <bhe@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: x86@kernel.org
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Yinghai Lu <yinghai@kernel.org>
> Cc: Borislav Petkov <bp@suse.de>
> ---
> arch/x86/boot/compressed/kaslr.c | 53 +++++++++++++++++++++++++++++++---------
> 1 file changed, 42 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index 36ab429..5361abd 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -67,6 +67,10 @@ int mem_avoid_memmap_index;
> extern unsigned long get_cmd_line_ptr(void);
>
>
> +/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
> +unsigned long long mem_limit = ULLONG_MAX;
I would either make this 0 or ULLONG_MAX - 1 (see below).
> +
> +
> enum mem_avoid_index {
> MEM_AVOID_ZO_RANGE = 0,
> MEM_AVOID_INITRD,
> @@ -117,15 +121,18 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
> return -EINVAL;
>
> switch (*p) {
> - case '@':
> - /* Skip this region, usable */
> - *size = 0;
> - *start = 0;
> case '#':
> case '$':
> case '!':
> *start = memparse(p + 1, &p);
> return 0;
> + case '@':
> + /* Skip this region, usable */
> + *size = 0;
Now it looks like we're intentionally falling through. A comment
should be included to indicate it.
> + default:
> + /* Avoid the region which is above the amount limit */
> + *start = 0;
> + return 0;
> }
>
> return -EINVAL;
> @@ -151,9 +158,14 @@ static void mem_avoid_memmap(char *str)
> if (rc < 0)
> break;
> str = k;
> - /* A usable region that should not be skipped */
> - if (size == 0)
> +
> + if (start == 0) {
> + /* Store the specified memory limit if size > 0 */
> + if (size > 0)
> + mem_limit = size;
> +
> continue;
> + }
>
> mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start;
> mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
> @@ -173,6 +185,7 @@ static int handle_mem_memmap(void)
> char tmp_cmdline[COMMAND_LINE_SIZE];
> size_t len = strlen((char *)args);
> char *param, *val;
> + u64 mem_size;
>
> len = (len >= COMMAND_LINE_SIZE) ? COMMAND_LINE_SIZE - 1 : len;
> memcpy(tmp_cmdline, args, len);
> @@ -195,8 +208,18 @@ static int handle_mem_memmap(void)
> return -1;
> }
>
> - if (!strcmp(param, "memmap"))
> + if (!strcmp(param, "memmap")) {
> mem_avoid_memmap(val);
> + } else if (!strcmp(param, "mem")) {
> + char *p = val;
> +
> + if (!strcmp(p, "nopentium"))
> + continue;
> + mem_size = memparse(p, &p);
> + if (mem_size == 0)
> + return -EINVAL;
> + mem_limit = mem_size;
> + }
> }
>
> return 0;
> @@ -432,7 +455,8 @@ static void process_e820_entry(struct e820entry *entry,
> {
> struct mem_vector region, overlap;
> struct slot_area slot_area;
> - unsigned long start_orig;
> + unsigned long start_orig, end;
> + struct e820entry cur_entry;
>
> /* Skip non-RAM entries. */
> if (entry->type != E820_RAM)
> @@ -446,8 +470,15 @@ static void process_e820_entry(struct e820entry *entry,
> if (entry->addr + entry->size < minimum)
> return;
>
> - region.start = entry->addr;
> - region.size = entry->size;
> + /* Ignore entries above memory limit */
> + end = min(entry->size + entry->addr - 1, mem_limit);
> + if (entry->addr >= end)
> + return;
> + cur_entry.addr = entry->addr;
> + cur_entry.size = end - entry->addr + 1;
> +
> + region.start = cur_entry.addr;
> + region.size = cur_entry.size;
I find the manipulation of entry->addr +/- 1 confusing; it should just
be mem_limit that is adjusted:
end = min(entry->size + entry->addr, mem_limit + 1);
And maybe to avoid mem_limit being giant by default, maybe have "0" be special?
cur_entry.addr = entry->addr;
if (mem_limit) {
unsigned long end = min(entry->size + entry->addr, mem_limit + 1);
if (entry->addr > end)
return;
cur_entry.size = end - entry->addr;
} else {
cur_entry.size = entry->size;
}
or something... and maybe move the whole thing earlier so other tests
that examine entry->size are checked with the new adjusted value.
-Kees
>
> /* Give up if slot area array is full. */
> while (slot_area_index < MAX_SLOT_AREA) {
> @@ -461,7 +492,7 @@ static void process_e820_entry(struct e820entry *entry,
> region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
>
> /* Did we raise the address above this e820 region? */
> - if (region.start > entry->addr + entry->size)
> + if (region.start > cur_entry.addr + cur_entry.size)
> return;
>
> /* Reduce size by any delta from the original address. */
> --
> 2.5.5
>
--
Kees Cook
Pixel Security
[toc] | [prev] | [next] | [standalone]
| From | Baoquan He <bhe@redhat.com> |
|---|---|
| Date | 2017-04-19 01:20 +0200 |
| Subject | Re: [PATCH 3/4] KASLR: Handle memory limit specified by memmap and mem option |
| Message-ID | <txKzD-3PB-5@gated-at.bofh.it> |
| In reply to | #1625642 |
On 04/18/17 at 01:36pm, Kees Cook wrote:
> On Mon, Apr 17, 2017 at 6:34 AM, Baoquan He <bhe@redhat.com> wrote:
> > Option mem= will limit the max address system can use. Any memory
> > region above the limit will be removed. And memmap=nn[KMG] which
> > has no offset specified has the same behaviour as mem=. KASLR need
> > consider this when choose the random position for decompressing
> > kernel. Do it in this patch.
> >
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: x86@kernel.org
> > Cc: Kees Cook <keescook@chromium.org>
> > Cc: Yinghai Lu <yinghai@kernel.org>
> > Cc: Borislav Petkov <bp@suse.de>
> > ---
> > arch/x86/boot/compressed/kaslr.c | 53 +++++++++++++++++++++++++++++++---------
> > 1 file changed, 42 insertions(+), 11 deletions(-)
> >
> > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> > index 36ab429..5361abd 100644
> > --- a/arch/x86/boot/compressed/kaslr.c
> > +++ b/arch/x86/boot/compressed/kaslr.c
> > @@ -67,6 +67,10 @@ int mem_avoid_memmap_index;
> > extern unsigned long get_cmd_line_ptr(void);
> >
> >
> > +/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
> > +unsigned long long mem_limit = ULLONG_MAX;
>
> I would either make this 0 or ULLONG_MAX - 1 (see below).
I prefer "ULLONG_MAX-1". Please see reason below
>
> > +
> > +
> > enum mem_avoid_index {
> > MEM_AVOID_ZO_RANGE = 0,
> > MEM_AVOID_INITRD,
> > @@ -117,15 +121,18 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
> > return -EINVAL;
> >
> > switch (*p) {
> > - case '@':
> > - /* Skip this region, usable */
> > - *size = 0;
> > - *start = 0;
> > case '#':
> > case '$':
> > case '!':
> > *start = memparse(p + 1, &p);
> > return 0;
> > + case '@':
> > + /* Skip this region, usable */
> > + *size = 0;
>
> Now it looks like we're intentionally falling through. A comment
> should be included to indicate it.
Yes, as I replied in patch 2/4, it's intended. Will add comment to
indicate.
>
> > + default:
> > + /* Avoid the region which is above the amount limit */
> > + *start = 0;
> > + return 0;
> > }
> >
> > return -EINVAL;
> > @@ -151,9 +158,14 @@ static void mem_avoid_memmap(char *str)
> > if (rc < 0)
> > break;
> > str = k;
> > - /* A usable region that should not be skipped */
> > - if (size == 0)
> > +
> > + if (start == 0) {
> > + /* Store the specified memory limit if size > 0 */
> > + if (size > 0)
> > + mem_limit = size;
> > +
> > continue;
> > + }
> >
> > mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start;
> > mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
> > @@ -173,6 +185,7 @@ static int handle_mem_memmap(void)
> > char tmp_cmdline[COMMAND_LINE_SIZE];
> > size_t len = strlen((char *)args);
> > char *param, *val;
> > + u64 mem_size;
> >
> > len = (len >= COMMAND_LINE_SIZE) ? COMMAND_LINE_SIZE - 1 : len;
> > memcpy(tmp_cmdline, args, len);
> > @@ -195,8 +208,18 @@ static int handle_mem_memmap(void)
> > return -1;
> > }
> >
> > - if (!strcmp(param, "memmap"))
> > + if (!strcmp(param, "memmap")) {
> > mem_avoid_memmap(val);
> > + } else if (!strcmp(param, "mem")) {
> > + char *p = val;
> > +
> > + if (!strcmp(p, "nopentium"))
> > + continue;
> > + mem_size = memparse(p, &p);
> > + if (mem_size == 0)
> > + return -EINVAL;
> > + mem_limit = mem_size;
> > + }
> > }
> >
> > return 0;
> > @@ -432,7 +455,8 @@ static void process_e820_entry(struct e820entry *entry,
> > {
> > struct mem_vector region, overlap;
> > struct slot_area slot_area;
> > - unsigned long start_orig;
> > + unsigned long start_orig, end;
> > + struct e820entry cur_entry;
> >
> > /* Skip non-RAM entries. */
> > if (entry->type != E820_RAM)
> > @@ -446,8 +470,15 @@ static void process_e820_entry(struct e820entry *entry,
> > if (entry->addr + entry->size < minimum)
> > return;
> >
> > - region.start = entry->addr;
> > - region.size = entry->size;
> > + /* Ignore entries above memory limit */
> > + end = min(entry->size + entry->addr - 1, mem_limit);
> > + if (entry->addr >= end)
> > + return;
> > + cur_entry.addr = entry->addr;
> > + cur_entry.size = end - entry->addr + 1;
> > +
> > + region.start = cur_entry.addr;
> > + region.size = cur_entry.size;
>
> I find the manipulation of entry->addr +/- 1 confusing; it should just
> be mem_limit that is adjusted:
>
> end = min(entry->size + entry->addr, mem_limit + 1);
The first one is preferred. Since if no memory limit specifed, we still have
a limit, 64T-1 or UULONG_MAX -1, in logic more understandable. And in
code lines it's less.
Will change with your suggestion.
Thanks a log for your comments!
>
> And maybe to avoid mem_limit being giant by default, maybe have "0" be special?
>
> cur_entry.addr = entry->addr;
> if (mem_limit) {
> unsigned long end = min(entry->size + entry->addr, mem_limit + 1);
> if (entry->addr > end)
> return;
> cur_entry.size = end - entry->addr;
> } else {
> cur_entry.size = entry->size;
> }
>
> or something... and maybe move the whole thing earlier so other tests
> that examine entry->size are checked with the new adjusted value.
>
> -Kees
>
> >
> > /* Give up if slot area array is full. */
> > while (slot_area_index < MAX_SLOT_AREA) {
> > @@ -461,7 +492,7 @@ static void process_e820_entry(struct e820entry *entry,
> > region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
> >
> > /* Did we raise the address above this e820 region? */
> > - if (region.start > entry->addr + entry->size)
> > + if (region.start > cur_entry.addr + cur_entry.size)
> > return;
> >
> > /* Reduce size by any delta from the original address. */
> > --
> > 2.5.5
> >
>
>
>
> --
> Kees Cook
> Pixel Security
[toc] | [prev] | [next] | [standalone]
| From | Baoquan He <bhe@redhat.com> |
|---|---|
| Date | 2017-04-19 03:00 +0200 |
| Subject | Re: [PATCH 3/4] KASLR: Handle memory limit specified by memmap and mem option |
| Message-ID | <txM8p-4NM-1@gated-at.bofh.it> |
| In reply to | #1625642 |
On 04/19/17 at 08:50am, Baoquan He wrote:
> On 04/18/17 at 01:36pm, Kees Cook wrote:
> > On Mon, Apr 17, 2017 at 6:34 AM, Baoquan He <bhe@redhat.com> wrote:
> > > @@ -432,7 +455,8 @@ static void process_e820_entry(struct e820entry *entry,
> > > {
> > > struct mem_vector region, overlap;
> > > struct slot_area slot_area;
> > > - unsigned long start_orig;
> > > + unsigned long start_orig, end;
> > > + struct e820entry cur_entry;
> > >
> > > /* Skip non-RAM entries. */
> > > if (entry->type != E820_RAM)
> > > @@ -446,8 +470,15 @@ static void process_e820_entry(struct e820entry *entry,
> > > if (entry->addr + entry->size < minimum)
> > > return;
> > >
> > > - region.start = entry->addr;
> > > - region.size = entry->size;
> > > + /* Ignore entries above memory limit */
> > > + end = min(entry->size + entry->addr - 1, mem_limit);
> > > + if (entry->addr >= end)
> > > + return;
> > > + cur_entry.addr = entry->addr;
> > > + cur_entry.size = end - entry->addr + 1;
> > > +
> > > + region.start = cur_entry.addr;
> > > + region.size = cur_entry.size;
> >
> > I find the manipulation of entry->addr +/- 1 confusing; it should just
> > be mem_limit that is adjusted:
> >
> > end = min(entry->size + entry->addr, mem_limit + 1);
>
> Oh, it should be like that. E.g if specify mem=4096M, it means available
^not
> memory region are 0~4096M-1, or [0, 4096M). Here mem_limit = 4096M.
> Adding 1 could make it wrong.
>
> >
> > And maybe to avoid mem_limit being giant by default, maybe have "0" be special?
> >
> > cur_entry.addr = entry->addr;
> > if (mem_limit) {
> > unsigned long end = min(entry->size + entry->addr, mem_limit + 1);
> > if (entry->addr > end)
> > return;
> > cur_entry.size = end - entry->addr;
> > } else {
> > cur_entry.size = entry->size;
> > }
> >
> > or something... and maybe move the whole thing earlier so other tests
> > that examine entry->size are checked with the new adjusted value.
>
> Sorry, forget replying to this comment. I am fine with moving it
> earlier. In fact I put it here because there are many non-RAM e820
> entries below 4G, like ACPI, for them we even don't need check limit
> by the help of below check filtering. Maybe move it after below check?
>
> /* Skip non-RAM entries. */
> if (entry->type != E820_RAM)
> return;
>
> >
> > -Kees
> >
> > >
> > > /* Give up if slot area array is full. */
> > > while (slot_area_index < MAX_SLOT_AREA) {
> > > @@ -461,7 +492,7 @@ static void process_e820_entry(struct e820entry *entry,
> > > region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
> > >
> > > /* Did we raise the address above this e820 region? */
> > > - if (region.start > entry->addr + entry->size)
> > > + if (region.start > cur_entry.addr + cur_entry.size)
> > > return;
> > >
> > > /* Reduce size by any delta from the original address. */
> > > --
> > > 2.5.5
> > >
> >
> >
> >
> > --
> > Kees Cook
> > Pixel Security
[toc] | [prev] | [next] | [standalone]
| From | Baoquan He <bhe@redhat.com> |
|---|---|
| Date | 2017-04-19 03:00 +0200 |
| Subject | Re: [PATCH 3/4] KASLR: Handle memory limit specified by memmap and mem option |
| Message-ID | <txM8p-4NM-3@gated-at.bofh.it> |
| In reply to | #1625642 |
On 04/18/17 at 01:36pm, Kees Cook wrote:
> On Mon, Apr 17, 2017 at 6:34 AM, Baoquan He <bhe@redhat.com> wrote:
> > @@ -432,7 +455,8 @@ static void process_e820_entry(struct e820entry *entry,
> > {
> > struct mem_vector region, overlap;
> > struct slot_area slot_area;
> > - unsigned long start_orig;
> > + unsigned long start_orig, end;
> > + struct e820entry cur_entry;
> >
> > /* Skip non-RAM entries. */
> > if (entry->type != E820_RAM)
> > @@ -446,8 +470,15 @@ static void process_e820_entry(struct e820entry *entry,
> > if (entry->addr + entry->size < minimum)
> > return;
> >
> > - region.start = entry->addr;
> > - region.size = entry->size;
> > + /* Ignore entries above memory limit */
> > + end = min(entry->size + entry->addr - 1, mem_limit);
> > + if (entry->addr >= end)
> > + return;
> > + cur_entry.addr = entry->addr;
> > + cur_entry.size = end - entry->addr + 1;
> > +
> > + region.start = cur_entry.addr;
> > + region.size = cur_entry.size;
>
> I find the manipulation of entry->addr +/- 1 confusing; it should just
> be mem_limit that is adjusted:
>
> end = min(entry->size + entry->addr, mem_limit + 1);
Oh, it should be like that. E.g if specify mem=4096M, it means available
memory region are 0~4096M-1, or [0, 4096M). Here mem_limit = 4096M.
Adding 1 could make it wrong.
>
> And maybe to avoid mem_limit being giant by default, maybe have "0" be special?
>
> cur_entry.addr = entry->addr;
> if (mem_limit) {
> unsigned long end = min(entry->size + entry->addr, mem_limit + 1);
> if (entry->addr > end)
> return;
> cur_entry.size = end - entry->addr;
> } else {
> cur_entry.size = entry->size;
> }
>
> or something... and maybe move the whole thing earlier so other tests
> that examine entry->size are checked with the new adjusted value.
Sorry, forget replying to this comment. I am fine with moving it
earlier. In fact I put it here because there are many non-RAM e820
entries below 4G, like ACPI, for them we even don't need check limit
by the help of below check filtering. Maybe move it after below check?
/* Skip non-RAM entries. */
if (entry->type != E820_RAM)
return;
>
> -Kees
>
> >
> > /* Give up if slot area array is full. */
> > while (slot_area_index < MAX_SLOT_AREA) {
> > @@ -461,7 +492,7 @@ static void process_e820_entry(struct e820entry *entry,
> > region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
> >
> > /* Did we raise the address above this e820 region? */
> > - if (region.start > entry->addr + entry->size)
> > + if (region.start > cur_entry.addr + cur_entry.size)
> > return;
> >
> > /* Reduce size by any delta from the original address. */
> > --
> > 2.5.5
> >
>
>
>
> --
> Kees Cook
> Pixel Security
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