EVM: fix the evm= __setup handler return value

stable inclusion
from stable-v5.10.110
commit d788ad472f83fc92df76deb7fff738d4d69329a2
bugzilla: https://gitee.com/openeuler/kernel/issues/I574AL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d788ad472f83fc92df76deb7fff738d4d69329a2

--------------------------------

[ Upstream commit f2544f5e ]

__setup() handlers should return 1 if the parameter is handled.
Returning 0 causes the entire string to be added to init's
environment strings (limited to 32 strings), unnecessarily polluting it.

Using the documented string "evm=fix" causes an Unknown parameter message:
  Unknown kernel command line parameters
  "BOOT_IMAGE=/boot/bzImage-517rc5 evm=fix", will be passed to user space.

and that string is added to init's environment string space:
  Run /sbin/init as init process
    with arguments:
     /sbin/init
    with environment:
     HOME=/
     TERM=linux
     BOOT_IMAGE=/boot/bzImage-517rc5
     evm=fix

With this change, using "evm=fix" acts as expected and an invalid
option ("evm=evm") causes a warning to be printed:
  evm: invalid "evm" mode
but init's environment is not polluted with this string, as expected.

Fixes: 7102ebcd ("evm: permit only valid security.evm xattrs to be updated")
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Reported-by: NIgor Zhbanov <i.zhbanov@omprussia.ru>
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru
Signed-off-by: NMimi Zohar <zohar@linux.ibm.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

security/integrity/evm/evm_main.c

@@ -70,7 +70,7 @@ static int __init evm_set_param(char *str)
 	else
 		pr_err("invalid \"%s\" mode", str);
 
-	return 0;
+	return 1;
 }
 __setup("evm=", evm_set_param);