Smack: handle zero-length security labels without panic
Zero-length security labels are invalid but kernel should handle them.
This patch fixes kernel panic after setting zero-length security labels:
# attr -S -s "SMACK64" -V "" file
And after writing zero-length string into smackfs files syslog and onlycp:
# python -c 'import os; os.write(1, "")' > /smack/syslog
The problem is caused by brain-damaged logic in function smk_parse_smack()
which takes pointer to buffer and its length but if length below or equal zero
it thinks that the buffer is zero-terminated. Unfortunately callers of this
function are widely used and proper fix requires serious refactoring.
Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@samsung.com>
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index b11ab23..afa5ad0 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -923,7 +923,7 @@
rc = -EPERM;
if (rc == 0 && check_import) {
- skp = smk_import_entry(value, size);
+ skp = size ? smk_import_entry(value, size) : NULL;
if (skp == NULL || (check_star &&
(skp == &smack_known_star || skp == &smack_known_web)))
rc = -EINVAL;
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 3c720ff..56a1439 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -1677,7 +1677,7 @@
if (smack_onlycap != NULL && smack_onlycap != skp)
return -EPERM;
- data = kzalloc(count, GFP_KERNEL);
+ data = kzalloc(count + 1, GFP_KERNEL);
if (data == NULL)
return -ENOMEM;
@@ -2228,7 +2228,7 @@
if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;
- data = kzalloc(count, GFP_KERNEL);
+ data = kzalloc(count + 1, GFP_KERNEL);
if (data == NULL)
return -ENOMEM;