linux-kernel - [PATCH] x86/mm/ident_map: Check for errors from ident_pud

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Message-Id: <20201027230648.1885111-1-nivedita@alum.mit.edu>
Date:   Tue, 27 Oct 2020 19:06:48 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Joerg Roedel <jroedel@...e.de>, linux-kernel@...r.kernel.org
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 <nivedita@...m.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