linux-kernel - [PATCH v3 05/17] arm64, hibernate: check pgd table allocation

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Message-Id: <20190821183204.23576-6-pasha.tatashin@soleen.com>
Date:   Wed, 21 Aug 2019 14:31:52 -0400
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     pasha.tatashin@...een.com, jmorris@...ei.org, sashal@...nel.org,
        ebiederm@...ssion.com, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org, corbet@....net,
        catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org, marc.zyngier@....com,
        james.morse@....com, vladimir.murzin@....com,
        matthias.bgg@...il.com, bhsharma@...hat.com, linux-mm@...ck.org,
        mark.rutland@....com
Subject: [PATCH v3 05/17] arm64, hibernate: check pgd table allocation

There is a bug in create_safe_exec_page(), when page table is allocated
it is not checked that table is allocated successfully:

But it is dereferenced in: pgd_none(READ_ONCE(*pgdp)).

Another issue, is that phys_to_ttbr() uses an offset in page table instead
of pgd directly.

So, allocate page table, check that allocation was successful, and use it
directly to set ttbr0_el1.

Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
---
 arch/arm64/kernel/hibernate.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
index ee34a06d8a35..750ecc7f2cbe 100644
--- a/arch/arm64/kernel/hibernate.c
+++ b/arch/arm64/kernel/hibernate.c
@@ -199,6 +199,7 @@ static int create_safe_exec_page(void *src_start, size_t length,
 				 phys_addr_t *phys_dst_addr)
 {
 	void *page = (void *)get_safe_page(GFP_ATOMIC);
+	pgd_t *trans_pgd;
 	pgd_t *pgdp;
 	pud_t *pudp;
 	pmd_t *pmdp;
@@ -210,7 +211,11 @@ static int create_safe_exec_page(void *src_start, size_t length,
 	memcpy(page, src_start, length);
 	__flush_icache_range((unsigned long)page, (unsigned long)page + length);
 
-	pgdp = pgd_offset_raw((void *)get_safe_page(GFP_ATOMIC), dst_addr);
+	trans_pgd = (void *)get_safe_page(GFP_ATOMIC);
+	if (!trans_pgd)
+		return -ENOMEM;
+
+	pgdp = pgd_offset_raw(trans_pgd, dst_addr);
 	if (pgd_none(READ_ONCE(*pgdp))) {
 		pudp = (void *)get_safe_page(GFP_ATOMIC);
 		if (!pudp)
@@ -251,7 +256,7 @@ static int create_safe_exec_page(void *src_start, size_t length,
 	 */
 	cpu_set_reserved_ttbr0();
 	local_flush_tlb_all();
-	write_sysreg(phys_to_ttbr(virt_to_phys(pgdp)), ttbr0_el1);
+	write_sysreg(phys_to_ttbr(virt_to_phys(trans_pgd)), ttbr0_el1);
 	isb();
 
 	*phys_dst_addr = virt_to_phys(page);
-- 
2.23.0