+ mm-mmap-return-1-from-stack_guard_gap-__setup-handler.patch added to -mm tree

+ mm-mmap-return-1-from-stack_guard_gap-__setup-handler.patch added to -mm tree

[Andrew Morton]

The patch titled
     Subject: mm/mmap: return 1 from stack_guard_gap __setup() handler
has been added to the -mm tree.  Its filename is
     mm-mmap-return-1-from-stack_guard_gap-__setup-handler.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-mmap-return-1-from-stack_guard_gap-__setup-handler.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-mmap-return-1-from-stack_guard_gap-__setup-handler.patch

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------------------------------------------------------
From: Randy Dunlap <rdunlap@infradead.org>
Subject: 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/20220222005817.11087-1-rdunlap@infradead.org
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru
Fixes: 1be7107fbe18e ("mm: larger stack guard gap, between vmas")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: Igor Zhbanov <i.zhbanov@omprussia.ru>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mmap.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/mmap.c~mm-mmap-return-1-from-stack_guard_gap-__setup-handler
+++ a/mm/mmap.c
@@ -2557,7 +2557,7 @@ static int __init cmdline_parse_stack_gu
 	if (!*endptr)
 		stack_guard_gap = val << PAGE_SHIFT;
 
-	return 0;
+	return 1;
 }
 __setup("stack_guard_gap=", cmdline_parse_stack_guard_gap);
 
_

Patches currently in -mm which might be from rdunlap@infradead.org are

mm-memcontrol-return-1-from-cgroupmemory-__setup-handler.patch
mm-mmap-return-1-from-stack_guard_gap-__setup-handler.patch
docs-sysctl-kernel-add-missing-bit-to-panic_print-fix.patch