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

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

[Arvind Sankar]

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 <nivedita@alum.mit.edu>
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

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

[Joerg Roedel]

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 <nivedita@alum.mit.edu>
> 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 <jroedel@suse.de>

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

[tip-bot2 for Arvind Sankar]

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 <nivedita@alum.mit.edu>
AuthorDate:    Tue, 27 Oct 2020 19:06:48 -04:00
Committer:     Borislav Petkov <bp@suse.de>
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 <nivedita@alum.mit.edu>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lkml.kernel.org/r/20201027230648.1885111-1-nivedita@alum.mit.edu
---
 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));
 	}