[PATCH 01/14] uaccess: fix integer overflow on access_ok()

Arnd Bergmann
2022-02-14T16:35:59Z

From: Arnd Bergmann <arnd@arndb.de>

Three architectures check the end of a user access against the
address limit without taking a possible overflow into account.
Passing a negative length or another overflow in here returns
success when it should not.

Use the most common correct implementation here, which optimizes
for a constant 'size' argument, and turns the common case into a
single comparison.

Cc: stable@vger.kernel.org
Fixes: da551281947c ("csky: User access")
Fixes: f663b60f5215 ("microblaze: Fix uaccess_ok macro")
Fixes: 7567746e1c0d ("Hexagon: Add user access functions")
Reported-by: David Laight <David.Laight@aculab.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
arch/csky/include/asm/uaccess.h | 7 +++----
arch/hexagon/include/asm/uaccess.h | 18 +++++++++---------
arch/microblaze/include/asm/uaccess.h | 19 ++++---------------
3 files changed, 16 insertions(+), 28 deletions(-)

diff --git a/arch/csky/include/asm/uaccess.h b/arch/csky/include/asm/uaccess.h
index c40f06ee8d3e..ac5a54f57d40 100644
--- a/arch/csky/include/asm/uaccess.h
+++ b/arch/csky/include/asm/uaccess.h
@@ -3,14 +3,13 @@
#ifndef __ASM_CSKY_UACCESS_H
#define __ASM_CSKY_UACCESS_H

-#define user_addr_max() \
- (uaccess_kernel() ? KERNEL_DS.seg : get_fs().seg)
+#define user_addr_max() (current_thread_info()->addr_limit.seg)

static inline int __access_ok(unsigned long addr, unsigned long size)
{
- unsigned long limit = current_thread_info()->addr_limit.seg;
+ unsigned long limit = user_addr_max();

- return ((addr < limit) && ((addr + size) < limit));
+ return (size <= limit) && (addr <= (limit - size));
}
#define __access_ok __access_ok

diff --git a/arch/hexagon/include/asm/uaccess.h b/arch/hexagon/include/asm/uaccess.h
index ef5bfef8d490..719ba3f3c45c 100644
--- a/arch/hexagon/include/asm/uaccess.h
+++ b/arch/hexagon/include/asm/uaccess.h
@@ -25,17 +25,17 @@
* Returns true (nonzero) if the memory block *may* be valid, false (zero)
* if it is definitely invalid.
*
- * User address space in Hexagon, like x86, goes to 0xbfffffff, so the
- * simple MSB-based tests used by MIPS won't work. Some further
- * optimization is probably possible here, but for now, keep it
- * reasonably simple and not *too* slow. After all, we've got the
- * MMU for backup.
*/
+#define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg)
+#define user_addr_max() (uaccess_kernel() ? ~0UL : TASK_SIZE)

-#define __access_ok(addr, size) \
- ((get_fs().seg == KERNEL_DS.seg) || \
- (((unsigned long)addr < get_fs().seg) && \
- (unsigned long)size < (get_fs().seg - (unsigned long)addr)))
+static inline int __access_ok(unsigned long addr, unsigned long size)
+{
+ unsigned long limit = TASK_SIZE;
+
+ return (size <= limit) && (addr <= (limit - size));
+}
+#define __access_ok __access_ok

/*
* When a kernel-mode page fault is taken, the faulting instruction
diff --git a/arch/microblaze/include/asm/uaccess.h b/arch/microblaze/include/asm/uaccess.h
index d2a8ef9f8978..5b6e0e7788f4 100644
--- a/arch/microblaze/include/asm/uaccess.h
+++ b/arch/microblaze/include/asm/uaccess.h
@@ -39,24 +39,13 @@

# define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg)

-static inline int access_ok(const void __user *addr, unsigned long size)
+static inline int __access_ok(unsigned long addr, unsigned long size)
{
- if (!size)
- goto ok;
+ unsigned long limit = user_addr_max();

- if ((get_fs().seg < ((unsigned long)addr)) ||
- (get_fs().seg < ((unsigned long)addr + size - 1))) {
- pr_devel("ACCESS fail at 0x%08x (size 0x%x), seg 0x%08x\n",
- (__force u32)addr, (u32)size,
- (u32)get_fs().seg);
- return 0;
- }
-ok:
- pr_devel("ACCESS OK at 0x%08x (size 0x%x), seg 0x%08x\n",
- (__force u32)addr, (u32)size,
- (u32)get_fs().seg);
- return 1;
+ return (size <= limit) && (addr <= (limit - size));
}
+#define access_ok(addr, size) __access_ok((unsigned long)addr, size)

# define __FIXUP_SECTION ".section .fixup,\"ax\"\n"
# define __EX_TABLE_SECTION ".section __ex_table,\"a\"\n"
--
2.29.2