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Date:   Mon,  4 Dec 2023 10:32:23 +0800
From:   Kunwu Chan <chentao@...inos.cn>
To:     mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu
Cc:     kunwu.chan@...mail.com, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, Kunwu Chan <chentao@...inos.cn>
Subject: [PATCH v3] powerpc/mm: Fix null-pointer dereference in pgtable_cache_add

kasprintf() returns a pointer to dynamically allocated memory
which can be NULL upon failure. Ensure the allocation was successful
by checking the pointer validity.

Suggested-by: Christophe Leroy <christophe.leroy@...roup.eu>
Suggested-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Kunwu Chan <chentao@...inos.cn>
---
v2: Use "panic" instead of "return"
v3: Merge two "panic" to one
---
 arch/powerpc/mm/init-common.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/mm/init-common.c b/arch/powerpc/mm/init-common.c
index 119ef491f797..d3a7726ecf51 100644
--- a/arch/powerpc/mm/init-common.c
+++ b/arch/powerpc/mm/init-common.c
@@ -126,7 +126,7 @@ void pgtable_cache_add(unsigned int shift)
 	 * as to leave enough 0 bits in the address to contain it. */
 	unsigned long minalign = max(MAX_PGTABLE_INDEX_SIZE + 1,
 				     HUGEPD_SHIFT_MASK + 1);
-	struct kmem_cache *new;
+	struct kmem_cache *new = NULL;
 
 	/* It would be nice if this was a BUILD_BUG_ON(), but at the
 	 * moment, gcc doesn't seem to recognize is_power_of_2 as a
@@ -139,7 +139,8 @@ void pgtable_cache_add(unsigned int shift)
 
 	align = max_t(unsigned long, align, minalign);
 	name = kasprintf(GFP_KERNEL, "pgtable-2^%d", shift);
-	new = kmem_cache_create(name, table_size, align, 0, ctor(shift));
+	if (name)
+		new = kmem_cache_create(name, table_size, align, 0, ctor(shift));
 	if (!new)
 		panic("Could not allocate pgtable cache for order %d", shift);
 
-- 
2.34.1

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