mm/mmap: return 1 from stack_guard_gap __setup() handler

__setup() handlers should return 1 if the command line option is handled
and 0 if not (or maybe never return 0; it just pollutes init's
environment).  This prevents:

  Unknown kernel command line parameters \
  "BOOT_IMAGE=/boot/bzImage-517rc5 stack_guard_gap=100", will be \
  passed to user space.

  Run /sbin/init as init process
   with arguments:
     /sbin/init
   with environment:
     HOME=/
     TERM=linux
     BOOT_IMAGE=/boot/bzImage-517rc5
     stack_guard_gap=100

Return 1 to indicate that the boot option has been handled.

Note that there is no warning message if someone enters:
	stack_guard_gap=anything_invalid
and 'val' and stack_guard_gap are both set to 0 due to the use of
simple_strtoul(). This could be improved by using kstrtoxxx() and
checking for an error.

It appears that having stack_guard_gap == 0 is valid (if unexpected) since
using "stack_guard_gap=0" on the kernel command line does that.

Link: https://lkml.kernel.org/r/[email protected]
Link: lore.kernel.org/r/[email protected]
Fixes: 1be7107fbe18e ("mm: larger stack guard gap, between vmas")
Signed-off-by: Randy Dunlap <[email protected]>
Reported-by: Igor Zhbanov <[email protected]>
Cc: Hugh Dickins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index f61a15474dd6..18875c216f8d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2557,7 +2557,7 @@ static int __init cmdline_parse_stack_guard_gap(char *p)
 	if (!*endptr)
 		stack_guard_gap = val << PAGE_SHIFT;
 
-	return 0;
+	return 1;
 }
 __setup("stack_guard_gap=", cmdline_parse_stack_guard_gap);