On 07.02.23 02:24, mawupeng wrote:
On 2023/2/7 1:05, David Hildenbrand wrote:
On 06.02.23 01:48, mawupeng wrote:
On 2023/2/4 1:14, David Hildenbrand wrote:
On 28.01.23 07:32, Wupeng Ma wrote:
From: Ma Wupeng <mawupeng1@xxxxxxxxxx>
While testing mlock, we have a problem if the len of mlock is ULONG_MAX.
The return value of mlock is zero. But nothing will be locked since the
len in do_mlock overflows to zero due to the following code in mlock:
len = PAGE_ALIGN(len + (offset_in_page(start)));
The same problem happens in munlock.
Add new check and return -EINVAL to fix this overflowing scenarios since
they are absolutely wrong.
Return 0 early to avoid burn a bunch of cpu cycles if len == 0.
Signed-off-by: Ma Wupeng <mawupeng1@xxxxxxxxxx>
---
mm/mlock.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/mm/mlock.c b/mm/mlock.c
index 7032f6dd0ce1..eb09968ba27f 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -478,8 +478,6 @@ static int apply_vma_lock_flags(unsigned long start, size_t len,
end = start + len;
if (end < start)
return -EINVAL;
- if (end == start)
- return 0;
vma = mas_walk(&mas);
if (!vma)
return -ENOMEM;
@@ -575,7 +573,13 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla
if (!can_do_mlock())
return -EPERM;
+ if (!len)
+ return 0;
+
len = PAGE_ALIGN(len + (offset_in_page(start)));
+ if (!len)
+ return -EINVAL;
+
start &= PAGE_MASK;
The "ordinary" overflows are detected in apply_vma_lock_flags(), correct?
Overflow is not checked anywhere however the ordinary return early if len == 0 is detected in apply_vma_lock_flags().
I meant the
end = start + len;
if (end < start)
return -EINVAL;
Essentially, what I wanted to double-check is that with your changes, we catch all kinds of overflows as documented in the man page, correct?
Oh i see. You are right, The "ordinary" overflows are detected for mlock/munlock in apply_vma_lock_flags().
Yes, we may need to update the man page for all these four syscalls.
E.g., mlock() already documents "EINVAL (mlock(), mlock2(), and
munlock()) The result of the addition addr+len was less than addr (e.g.,
the addition may have resulted in an overflow)."
Just to rephrase my question what I wanted to double-check: are we now
identifying all such overflows or are you aware of other corner cases?
--
Thanks,
David / dhildenb
