On 2023/3/20 18:54, David Hildenbrand wrote: > On 20.03.23 03:47, 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. > > Thinking again, wouldn't we reject mlock(0, ULONG_MAX) now as well? mlock will return 0 if len is zero which is the same w/o this patchset. Here is the calltrace if len is zero. mlock(len == 0) do_mlock(len == 0) if (!len) return 0 Sorry for wasting your time in the wrong v4. Here is the latest v5: https://patchwork.kernel.org/project/linux-mm/list/?series=732216 > >> >> Signed-off-by: Ma Wupeng <mawupeng1@xxxxxxxxxx> >> --- >> mm/mlock.c | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/mm/mlock.c b/mm/mlock.c >> index 617469fce96d..eb68476da497 100644 >> --- a/mm/mlock.c >> +++ b/mm/mlock.c >> @@ -568,6 +568,7 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla >> unsigned long locked; >> unsigned long lock_limit; >> int error = -ENOMEM; >> + size_t old_len = len; >> start = untagged_addr(start); >> @@ -577,6 +578,9 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla >> len = PAGE_ALIGN(len + (offset_in_page(start))); >> start &= PAGE_MASK; >> + if (old_len != 0 && len == 0) > > if (old_len && !len) > >> + return -EINVAL; >> + >> lock_limit = rlimit(RLIMIT_MEMLOCK); >> lock_limit >>= PAGE_SHIFT; >> locked = len >> PAGE_SHIFT; >> @@ -631,12 +635,16 @@ SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags) >> SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len) >> { >> int ret; >> + size_t old_len = len; >> start = untagged_addr(start); >> len = PAGE_ALIGN(len + (offset_in_page(start))); >> start &= PAGE_MASK; >> + if (old_len != 0 && len == 0) > > if (old_len && !len) > >> + return -EINVAL; >> + >> if (mmap_write_lock_killable(current->mm)) >> return -EINTR; >> ret = apply_vma_lock_flags(start, len, 0); >
