[PATCH 2/9] common/memsize.c: Fix get_effective_memsize() to check for overflow

Pali Rohár
2022-09-09T15:33:28Z

Ensure that top of RAM can be represented by phys_size_t type. If RAM is
too large or RAM base address is too upper then limit RAM size to prevent
address space overflow.

Signed-off-by: Pali Rohár <pali@kernel.org>
---
common/memsize.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/common/memsize.c b/common/memsize.c
index 31884acca0df..d11ed67632fb 100644
--- a/common/memsize.c
+++ b/common/memsize.c
@@ -94,11 +94,23 @@ long get_ram_size(long *base, long maxsize)

phys_size_t __weak get_effective_memsize(void)
{
+ phys_size_t ram_size = gd->ram_size;
+
+ /*
+ * Check for overflow and limit ram size to some representable value.
+ * It is required that ram_base + ram_size must be representable by
+ * phys_size_t type and must be aligned by direct access, therefore
+ * calculate it from last 4kB sector which should work as alignment
+ * on any platform.
+ */
+ if (gd->ram_base + ram_size < gd->ram_base)
+ ram_size = ((phys_size_t)~0xfffULL) - gd->ram_base;
+
#ifndef CONFIG_MAX_MEM_MAPPED
- return gd->ram_size;
+ return ram_size;
#else
/* limit stack to what we can reasonable map */
- return ((gd->ram_size > CONFIG_MAX_MEM_MAPPED) ?
- CONFIG_MAX_MEM_MAPPED : gd->ram_size);
+ return ((ram_size > CONFIG_MAX_MEM_MAPPED) ?
+ CONFIG_MAX_MEM_MAPPED : ram_size);
#endif
}
--
2.20.1