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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>
This commit is contained in:
Konstantin Khlebnikov 2014-08-07 20:52:43 +04:00 committed by Casey Schaufler
parent fd5c9d230d
commit b862e561ba
2 changed files with 3 additions and 3 deletions
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2
security/smack/smack_lsm.c
View File

@ -923,7 +923,7 @@ static int smack_inode_setxattr(struct dentry *dentry, const char *name,
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;

4
security/smack/smackfs.c
View File

@ -1677,7 +1677,7 @@ static ssize_t smk_write_onlycap(struct file *file, const char __user *buf,
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 @@ static ssize_t smk_write_syslog(struct file *file, const char __user *buf,
if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;
data = kzalloc(count, GFP_KERNEL);
data = kzalloc(count + 1, GFP_KERNEL);
if (data == NULL)
return -ENOMEM;