[PATCH] riscv: check leaf entry alignment in pageattr_pxd_entry()

[Austin Kim <austindh.kim@gmail.com>]

During page table walking, ensure the range being processed matches
the expected size of a leaf entry (P4D, PUD, or PMD). While pxd_addr_end() 
functions handle boundary checks, they do not inherently validate whether 
the entry is a leaf node of the expected size.

Add WARN_ON_ONCE() to detect misalignments or partial updates of huge 
pages. If a mismatch is detected, return -EINVAL to prevent potential
corruption of page table entries.

Signed-off-by: Austin Kim <austindh.kim@gmail.com>
---
 arch/riscv/mm/pageattr.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
index 3f76db3d2..1461bf77f 100644
--- a/arch/riscv/mm/pageattr.c
+++ b/arch/riscv/mm/pageattr.c
@@ -32,6 +32,8 @@ static int pageattr_p4d_entry(p4d_t *p4d, unsigned long addr,
 	p4d_t val = p4dp_get(p4d);
 
 	if (p4d_leaf(val)) {
+		if (WARN_ON_ONCE((next - addr) != P4D_SIZE))
+			return -EINVAL;
 		val = __p4d(set_pageattr_masks(p4d_val(val), walk));
 		set_p4d(p4d, val);
 	}
@@ -45,6 +47,8 @@ static int pageattr_pud_entry(pud_t *pud, unsigned long addr,
 	pud_t val = pudp_get(pud);
 
 	if (pud_leaf(val)) {
+		if (WARN_ON_ONCE((next - addr) != PUD_SIZE))
+			return -EINVAL;
 		val = __pud(set_pageattr_masks(pud_val(val), walk));
 		set_pud(pud, val);
 	}
@@ -58,6 +62,8 @@ static int pageattr_pmd_entry(pmd_t *pmd, unsigned long addr,
 	pmd_t val = pmdp_get(pmd);
 
 	if (pmd_leaf(val)) {
+		if (WARN_ON_ONCE((next - addr) != PMD_SIZE))
+			return -EINVAL;
 		val = __pmd(set_pageattr_masks(pmd_val(val), walk));
 		set_pmd(pmd, val);
 	}
-- 
2.34.1


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