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 617469fce96d..247ce396bb16 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -479,8 +479,6 @@ 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 = vma_iter_load(&vmi); if (!vma) return -ENOMEM; @@ -574,7 +572,13 @@ 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; lock_limit = rlimit(RLIMIT_MEMLOCK); @@ -634,7 +638,13 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len) start = untagged_addr(start); + if (!len) + return 0; + len = PAGE_ALIGN(len + (offset_in_page(start))); + if (!len) + return -EINVAL; + start &= PAGE_MASK; if (mmap_write_lock_killable(current->mm)) -- 2.25.1
