linux-hardening - [PATCH] pstore: ram_core: fix possible overflow in persistent_ram_init

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Message-ID: <20231105202936.25694-1-s.shtylyov@omp.ru>
Date: Sun, 5 Nov 2023 23:29:36 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Kees Cook <keescook@...omium.org>, Tony Luck <tony.luck@...el.com>,
	"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
	<linux-hardening@...r.kernel.org>
Subject: [PATCH] pstore: ram_core: fix possible overflow in persistent_ram_init_ecc()

In persistent_ram_init_ecc(), on 64-bit arches DIV_ROUND_UP() will return
64-bit value since persistent_ram_zone::buffer_size has type size_t which
is derived from the 64-bit *unsigned long*, while the ecc_blocks variable
this value gets assigned to has (always 32-bit) *int* type.  Even if that
value fits into *int* type, an overflow is still possible when calculating
the size_t typed ecc_total variable further below since there's no cast to
any 64-bit type before multiplication.  Declaring the ecc_blocks variable
as *unsigned long* should fix this mess...

Found by Linux Verification Center (linuxtesting.org) with the SVACE static
analysis tool.

Fixes: 9cc05ad97c57 ("staging: android: persistent_ram: refactor ecc support")
Signed-off-by: Sergey Shtylyov <s.shtylyov@....ru>
---
The patch is against the 'master' branch of Linus Torvalds' repo.

 fs/pstore/ram_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index 650e437b55e6..131c1923b8c0 100644
--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -190,7 +190,7 @@ static int persistent_ram_init_ecc(struct persistent_ram_zone *prz,
 {
 	int numerr;
 	struct persistent_ram_buffer *buffer = prz->buffer;
-	int ecc_blocks;
+	unsigned long ecc_blocks;
 	size_t ecc_total;

 	if (!ecc_info || !ecc_info->ecc_size)
-- 
2.26.3