From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiggers3@gmail.com (Eric Biggers) Date: Sat, 1 Apr 2017 14:34:28 -0700 Subject: [PATCH] KEYS: fix dereferencing NULL payload with nonzero length Message-ID: <20170401213428.17097-1-ebiggers3@gmail.com> To: linux-security-module@vger.kernel.org List-Id: linux-security-module.vger.kernel.org From: Eric Biggers sys_add_key() and the KEYCTL_UPDATE operation of sys_keyctl() allowed a NULL payload with nonzero length to be passed to the key type's ->preparse(), ->instantiate(), and/or ->update() methods. Various key types including asymmetric, cifs.idmap, cifs.spnego, and pkcs7_test did not handle this case, allowing an unprivileged user to trivially cause a NULL pointer dereference (kernel oops) if one of these key types was present. Fix it by doing the copy_from_user() when 'plen' is nonzero rather than when '_payload' is non-NULL, causing the syscall to fail with EFAULT as expected when an invalid buffer is specified. Cc: stable at vger.kernel.org # 2.6.10+ Signed-off-by: Eric Biggers --- security/keys/keyctl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index 52c34532c785..57447cd29154 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -99,7 +99,7 @@ SYSCALL_DEFINE5(add_key, const char __user *, _type, /* pull the payload in if one was supplied */ payload = NULL; - if (_payload) { + if (plen) { ret = -ENOMEM; payload = kmalloc(plen, GFP_KERNEL | __GFP_NOWARN); if (!payload) { @@ -324,7 +324,7 @@ long keyctl_update_key(key_serial_t id, /* pull the payload in if one was supplied */ payload = NULL; - if (_payload) { + if (plen) { ret = -ENOMEM; payload = kmalloc(plen, GFP_KERNEL); if (!payload) -- 2.12.1 -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html