[PATCH] mtd: parsers: qcom: fix offset/size overflow on large partitions

[Weigang He <geoffreyhe2@gmail.com>]

In parse_qcomsmem_part() the partition offset and size are computed as

	parts[j].offset = le32_to_cpu(pentry->offset) * mtd->erasesize;
	parts[j].size   = le32_to_cpu(pentry->length) * mtd->erasesize;

Both le32_to_cpu() and mtd->erasesize are 32-bit (u32). The multiply is
therefore evaluated in 32-bit arithmetic and the product is truncated to
32 bits before being widened and stored into the 64-bit (u64)
parts[j].offset / parts[j].size fields, so the 64-bit destinations are
never used at their full width.

The SMEM partition table is firmware-provided and the per-entry offset
and length are not bounds-checked against the device geometry (only
numparts is capped). On a sufficiently large flash, a partition whose
(offset|length) * erasesize is >= 2^32 gets a silently truncated
offset/size and is mapped to the wrong region of the master MTD, which
can overlap or extend into an unintended area.

Cast one operand to u64 so the multiplication is performed in 64-bit and
the result fits the 64-bit fields without truncation.

Found by static analysis tool CodeQL.

Fixes: 803eb124e1a6 ("mtd: parsers: Add Qcom SMEM parser")
Cc: stable@vger.kernel.org
Assisted-by: LLM codeql
Signed-off-by: Weigang He <geoffreyhe2@gmail.com>
---

Notes:
    Compile-tested only (ARCH=arm64 allmodconfig, W=1). Not tested on
    hardware, and there is no reproducer.
    
    The CodeQL query behind this report was synthesized with LLM assistance,
    and the fix and changelog were drafted with LLM assistance; I have
    reviewed them.

 drivers/mtd/parsers/qcomsmempart.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/parsers/qcomsmempart.c b/drivers/mtd/parsers/qcomsmempart.c
index d4fdc46a00730..1591aea48b280 100644
--- a/drivers/mtd/parsers/qcomsmempart.c
+++ b/drivers/mtd/parsers/qcomsmempart.c
@@ -143,9 +143,9 @@ static int parse_qcomsmem_part(struct mtd_info *mtd,
 			*c = tolower(*c);
 
 		parts[j].name = name;
-		parts[j].offset = le32_to_cpu(pentry->offset) * mtd->erasesize;
+		parts[j].offset = (u64)le32_to_cpu(pentry->offset) * mtd->erasesize;
 		parts[j].mask_flags = pentry->attr;
-		parts[j].size = le32_to_cpu(pentry->length) * mtd->erasesize;
+		parts[j].size = (u64)le32_to_cpu(pentry->length) * mtd->erasesize;
 		pr_debug("%d: %s offs=0x%08x size=0x%08x attr:0x%08x\n",
 			 i, pentry->name, le32_to_cpu(pentry->offset),
 			 le32_to_cpu(pentry->length), pentry->attr);

base-commit: 165768bb70265b5c38cf0b73fafd75be235f8b14
prerequisite-patch-id: c5a3be8688fd8e88a00352acb1374e91fcb52a03
prerequisite-patch-id: 67693e2c08624df0841619cc085ce9200f4385fc
prerequisite-patch-id: f3d73f7c19be7e952aa8061303f53f9a08576a88
prerequisite-patch-id: 541e578709d048f4c8115f1d926be2f2c03ecb0e
prerequisite-patch-id: f23f8e0693435497645805822d98a92e57fb46f3
prerequisite-patch-id: eae82895db8ba67018a777a91a283ad6bc4a55b2
prerequisite-patch-id: aed00f7502865e3f9262959d828eae4a4021108f
-- 
2.43.0