From d4eaa2837851db2bfed572898bfc17f9a9f9151e Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Thu, 4 Jun 2020 16:48:21 -0700 Subject: mm: add kvfree_sensitive() for freeing sensitive data objects For kvmalloc'ed data object that contains sensitive information like cryptographic keys, we need to make sure that the buffer is always cleared before freeing it. Using memset() alone for buffer clearing may not provide certainty as the compiler may compile it away. To be sure, the special memzero_explicit() has to be used. This patch introduces a new kvfree_sensitive() for freeing those sensitive data objects allocated by kvmalloc(). The relevant places where kvfree_sensitive() can be used are modified to use it. Fixes: 4f0882491a14 ("KEYS: Avoid false positive ENOMEM error on key read") Suggested-by: Linus Torvalds Signed-off-by: Waiman Long Signed-off-by: Andrew Morton Reviewed-by: Eric Biggers Acked-by: David Howells Cc: Jarkko Sakkinen Cc: James Morris Cc: "Serge E. Hallyn" Cc: Joe Perches Cc: Matthew Wilcox Cc: David Rientjes Cc: Uladzislau Rezki Link: http://lkml.kernel.org/r/20200407200318.11711-1-longman@redhat.com Signed-off-by: Linus Torvalds --- security/keys/internal.h | 11 ----------- security/keys/keyctl.c | 16 +++++----------- 2 files changed, 5 insertions(+), 22 deletions(-) (limited to 'security') diff --git a/security/keys/internal.h b/security/keys/internal.h index 6d0ca48ae9a5..153d35c20d3d 100644 --- a/security/keys/internal.h +++ b/security/keys/internal.h @@ -350,15 +350,4 @@ static inline void key_check(const struct key *key) #define key_check(key) do {} while(0) #endif - -/* - * Helper function to clear and free a kvmalloc'ed memory object. - */ -static inline void __kvzfree(const void *addr, size_t len) -{ - if (addr) { - memset((void *)addr, 0, len); - kvfree(addr); - } -} #endif /* _INTERNAL_H */ diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index 5e01192e222a..edde63a63007 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -142,10 +142,7 @@ SYSCALL_DEFINE5(add_key, const char __user *, _type, key_ref_put(keyring_ref); error3: - if (payload) { - memzero_explicit(payload, plen); - kvfree(payload); - } + kvfree_sensitive(payload, plen); error2: kfree(description); error: @@ -360,7 +357,7 @@ long keyctl_update_key(key_serial_t id, key_ref_put(key_ref); error2: - __kvzfree(payload, plen); + kvfree_sensitive(payload, plen); error: return ret; } @@ -914,7 +911,7 @@ can_read_key: */ if (ret > key_data_len) { if (unlikely(key_data)) - __kvzfree(key_data, key_data_len); + kvfree_sensitive(key_data, key_data_len); key_data_len = ret; continue; /* Allocate buffer */ } @@ -923,7 +920,7 @@ can_read_key: ret = -EFAULT; break; } - __kvzfree(key_data, key_data_len); + kvfree_sensitive(key_data, key_data_len); key_put_out: key_put(key); @@ -1225,10 +1222,7 @@ long keyctl_instantiate_key_common(key_serial_t id, keyctl_change_reqkey_auth(NULL); error2: - if (payload) { - memzero_explicit(payload, plen); - kvfree(payload); - } + kvfree_sensitive(payload, plen); error: return ret; } -- cgit v1.2.3-59-g8ed1b