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EVM: fix the evm= __setup handler return value

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__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: 7102ebcd65 ("evm: permit only valid security.evm xattrs to be updated")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: Igor Zhbanov <i.zhbanov@omprussia.ru>
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Randy Dunlap 2022-02-22 13:45:18 -08:00 committed by Mimi Zohar
parent cd3bc044af
commit f2544f5e6c
1 changed files with 1 additions and 1 deletions
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2
security/integrity/evm/evm_main.c
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@ -86,7 +86,7 @@ static int __init evm_set_fixmode(char *str)
else
pr_err("invalid \"%s\" mode", str);
return 0;
return 1;
}
__setup("evm=", evm_set_fixmode);