* [PATCH 1/2] mm/mmap.c: add more sanity checks to get_unmapped_area()
2020-03-23 13:29 [PATCH 0/2] mm/mmap: check mapping limits more strictly agordeev
@ 2020-03-23 13:29 ` agordeev
2020-03-23 13:29 ` [PATCH 2/2] mm/mmap.c: do not allow mappings outside of allowed limits agordeev
1 sibling, 0 replies; 5+ messages in thread
From: agordeev @ 2020-03-23 13:29 UTC (permalink / raw)
To: linux-kernel; +Cc: linux-mm, Alexander Gordeev
From: Alexander Gordeev <agordeev@linux.ibm.com>
Generic get_unmapped_area() function does sanity checks
of address and length of the area to be mapped. Yet, it
lacks checking against mmap_min_addr and mmap_end limits.
At the same time the default implementation of functions
arch_get_unmapped_area[_topdown]() and some architecture
callbacks do mmap_min_addr and mmap_end checks on its own.
Put additional checks into the generic code and do not let
architecture callbacks to get away with a possible area
outside of the allowed limits.
That could also relieve arch_get_unmapped_area[_topdown]()
callbacks of own address and length sanity checks.
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
---
mm/mmap.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index d681a20eb4ea..a0fcb5ca0e06 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2168,12 +2168,13 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
unsigned long (*get_area)(struct file *, unsigned long,
unsigned long, unsigned long, unsigned long);
+ const unsigned long mmap_end = arch_get_mmap_end(addr);
unsigned long error = arch_mmap_check(addr, len, flags);
if (error)
return error;
/* Careful about overflows.. */
- if (len > TASK_SIZE)
+ if (len > mmap_end - mmap_min_addr)
return -ENOMEM;
get_area = current->mm->get_unmapped_area;
@@ -2194,7 +2195,7 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
if (IS_ERR_VALUE(addr))
return addr;
- if (addr > TASK_SIZE - len)
+ if ((addr < mmap_min_addr) || (addr > mmap_end - len))
return -ENOMEM;
if (offset_in_page(addr))
return -EINVAL;
--
2.23.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH 2/2] mm/mmap.c: do not allow mappings outside of allowed limits
2020-03-23 13:29 [PATCH 0/2] mm/mmap: check mapping limits more strictly agordeev
2020-03-23 13:29 ` [PATCH 1/2] mm/mmap.c: add more sanity checks to get_unmapped_area() agordeev
@ 2020-03-23 13:29 ` agordeev
2020-04-21 2:59 ` Andrew Morton
1 sibling, 1 reply; 5+ messages in thread
From: agordeev @ 2020-03-23 13:29 UTC (permalink / raw)
To: linux-kernel; +Cc: linux-mm, Alexander Gordeev
From: Alexander Gordeev <agordeev@linux.ibm.com>
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.
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
---
mm/mmap.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index a0fcb5ca0e06..bd673a01b1d0 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -59,6 +59,14 @@
#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;
@@ -1366,6 +1374,7 @@ 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;
@@ -1388,8 +1397,12 @@ 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);
@@ -2050,15 +2063,6 @@ unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
return gap_end;
}
-
-#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.
*
--
2.23.0
^ permalink raw reply related [flat|nested] 5+ messages in thread