2020-10-28 21:42:02

by Arvind Sankar

Subject: [PATCH] x86/mm/ident_map: Check for errors from ident_pud_init()

Commit
ea3b5e60ce80 ("x86/mm/ident_map: Add 5-level paging support")
added ident_p4d_init() to support 5-level paging, but this function
doesn't check and return errors from ident_pud_init().

For example, the decompressor stub uses this code to create an identity
mapping. If it runs out of pages while trying to allocate a PMD
pagetable, the error will be currently ignored.

Fix this to propagate errors.

Signed-off-by: Arvind Sankar <[email protected]>
Fixes: ea3b5e60ce80 ("x86/mm/ident_map: Add 5-level paging support")
---
arch/x86/mm/ident_map.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
index fe7a12599d8e..5ecb0883cc88 100644
--- a/arch/x86/mm/ident_map.c
+++ b/arch/x86/mm/ident_map.c
@@ -62,6 +62,7 @@ static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,
unsigned long addr, unsigned long end)
{
unsigned long next;
+ int result;

for (; addr < end; addr = next) {
p4d_t *p4d = p4d_page + p4d_index(addr);
@@ -73,13 +74,17 @@ static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,

if (p4d_present(*p4d)) {
pud = pud_offset(p4d, 0);
- ident_pud_init(info, pud, addr, next);
+ result = ident_pud_init(info, pud, addr, next);
+ if (result)
+ return result;
continue;
}
pud = (pud_t *)info->alloc_pgt_page(info->context);
if (!pud)
return -ENOMEM;
- ident_pud_init(info, pud, addr, next);
+ result = ident_pud_init(info, pud, addr, next);
+ if (result)
+ return result;
set_p4d(p4d, __p4d(__pa(pud) | info->kernpg_flag));
}

--
2.26.2

2020-10-28 22:18:10

by tip-bot2 for Haifeng Xu

Subject: [tip: x86/mm] x86/mm/ident_map: Check for errors from ident_pud_init()

The following commit has been merged into the x86/mm branch of tip:

Commit-ID: 1fcd009102ee02e217f2e7635ab65517d785da8e
Gitweb: https://git.kernel.org/tip/1fcd009102ee02e217f2e7635ab65517d785da8e
Author: Arvind Sankar <[email protected]>
AuthorDate: Tue, 27 Oct 2020 19:06:48 -04:00
Committer: Borislav Petkov <[email protected]>
CommitterDate: Wed, 28 Oct 2020 14:48:30 +01:00

x86/mm/ident_map: Check for errors from ident_pud_init()

Commit

ea3b5e60ce80 ("x86/mm/ident_map: Add 5-level paging support")

added ident_p4d_init() to support 5-level paging, but this function
doesn't check and return errors from ident_pud_init().

For example, the decompressor stub uses this code to create an identity
mapping. If it runs out of pages while trying to allocate a PMD
pagetable, the error will be currently ignored.

Fix this to propagate errors.

[ bp: Space out statements for better readability. ]

Fixes: ea3b5e60ce80 ("x86/mm/ident_map: Add 5-level paging support")
Signed-off-by: Arvind Sankar <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Joerg Roedel <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
arch/x86/mm/ident_map.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
index fe7a125..968d700 100644
--- a/arch/x86/mm/ident_map.c
+++ b/arch/x86/mm/ident_map.c
@@ -62,6 +62,7 @@ static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,
unsigned long addr, unsigned long end)
{
unsigned long next;
+ int result;

for (; addr < end; addr = next) {
p4d_t *p4d = p4d_page + p4d_index(addr);
@@ -73,13 +74,20 @@ static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,

if (p4d_present(*p4d)) {
pud = pud_offset(p4d, 0);
- ident_pud_init(info, pud, addr, next);
+ result = ident_pud_init(info, pud, addr, next);
+ if (result)
+ return result;
+
continue;
}
pud = (pud_t *)info->alloc_pgt_page(info->context);
if (!pud)
return -ENOMEM;
- ident_pud_init(info, pud, addr, next);
+
+ result = ident_pud_init(info, pud, addr, next);
+ if (result)
+ return result;
+
set_p4d(p4d, __p4d(__pa(pud) | info->kernpg_flag));
}

2020-10-29 07:45:04

by Joerg Roedel

Subject: Re: [PATCH] x86/mm/ident_map: Check for errors from ident_pud_init()

On Tue, Oct 27, 2020 at 07:06:48PM -0400, Arvind Sankar wrote:
> Commit
> ea3b5e60ce80 ("x86/mm/ident_map: Add 5-level paging support")
> added ident_p4d_init() to support 5-level paging, but this function
> doesn't check and return errors from ident_pud_init().
>
> For example, the decompressor stub uses this code to create an identity
> mapping. If it runs out of pages while trying to allocate a PMD
> pagetable, the error will be currently ignored.
>
> Fix this to propagate errors.
>
> Signed-off-by: Arvind Sankar <[email protected]>
> Fixes: ea3b5e60ce80 ("x86/mm/ident_map: Add 5-level paging support")
> ---
> arch/x86/mm/ident_map.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)

Reviewed-by: Joerg Roedel <[email protected]>