2020-04-15 21:41:21

by Alexander Gordeev

Subject: [PATCH RESEND 0/2] mm/mmap: check mapping address limits more strictly

The series is against linux-next

CC: [email protected]

Alexander Gordeev (2):
mm/mmap.c: add more sanity checks to get_unmapped_area()
mm/mmap.c: deny fixed mappings outside of allowed limits

mm/mmap.c | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)

--
1.8.3.1

2020-04-15 21:41:28

by Alexander Gordeev

Subject: [PATCH RESEND 2/2] mm/mmap.c: deny fixed mappings outside of allowed limits

It is possible to request a fixed mapping address below
mmap_min_addr and succeed. This update adds early checks
of mmap_min_addr and mmap_end boundaries and fixes the
above issue.

CC: [email protected]
Signed-off-by: Alexander Gordeev <[email protected]>
---
mm/mmap.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 5b22d47..9a16e25 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -62,6 +62,14 @@
#define arch_mmap_check(addr, len, flags) (0)
#endif

+#ifndef arch_get_mmap_end
+#define arch_get_mmap_end(addr) (TASK_SIZE)
+#endif
+
+#ifndef arch_get_mmap_base
+#define arch_get_mmap_base(addr, base) (base)
+#endif
+
#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
@@ -1369,6 +1377,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
unsigned long pgoff, unsigned long *populate,
struct list_head *uf)
{
+ const unsigned long mmap_end = arch_get_mmap_end(addr);
struct mm_struct *mm = current->mm;
int pkey = 0;

@@ -1391,8 +1400,12 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
if (flags & MAP_FIXED_NOREPLACE)
flags |= MAP_FIXED;

- if (!(flags & MAP_FIXED))
+ if (flags & MAP_FIXED) {
+ if ((addr < mmap_min_addr) || (addr > mmap_end))
+ return -ENOMEM;
+ } else {
addr = round_hint_to_min(addr);
+ }

/* Careful about overflows.. */
len = PAGE_ALIGN(len);
@@ -2089,14 +2102,6 @@ unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info)
return addr;
}

-#ifndef arch_get_mmap_end
-#define arch_get_mmap_end(addr) (TASK_SIZE)
-#endif
-
-#ifndef arch_get_mmap_base
-#define arch_get_mmap_base(addr, base) (base)
-#endif
-
/* Get an address range which is currently unmapped.
* For shmat() with addr=0.
*
--
1.8.3.1