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| author | Ahmed S. Darwish <darwish.07@gmail.com> | 2008-03-13 12:32:34 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-03-13 13:11:43 -0700 |
| commit | b500ce8d24d1f14426643da5f6fada28c1f60533 (patch) | |
| tree | 17b6084b29434a968f787e238548a843126e2ec3 /security/smack/smackfs.c | |
| parent | 93d74463d018ddf05c169ad399e62e90e0f82fc0 (diff) | |
| download | lwn-b500ce8d24d1f14426643da5f6fada28c1f60533.tar.gz lwn-b500ce8d24d1f14426643da5f6fada28c1f60533.zip | |
smackfs: do not trust `count' in inodes write()s
Smackfs write() implementation does not put a higher bound on the number of
bytes to copy from user-space. This may lead to a DOS attack if a malicious
`count' field is given.
Assure that given `count' is exactly the length needed for a /smack/load rule.
In case of /smack/cipso where the length is relative, assure that `count'
does not exceed the size needed for a buffer representing maximum possible
number of CIPSO 2.2 categories.
Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'security/smack/smackfs.c')
| -rw-r--r-- | security/smack/smackfs.c | 31 |
1 files changed, 20 insertions, 11 deletions
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c index 358c92c1a153..afe7c9b0732a 100644 --- a/security/smack/smackfs.c +++ b/security/smack/smackfs.c @@ -81,10 +81,23 @@ static struct semaphore smack_write_sem; /* * Values for parsing cipso rules * SMK_DIGITLEN: Length of a digit field in a rule. - * SMK_CIPSOMEN: Minimum possible cipso rule length. + * SMK_CIPSOMIN: Minimum possible cipso rule length. + * SMK_CIPSOMAX: Maximum possible cipso rule length. */ #define SMK_DIGITLEN 4 -#define SMK_CIPSOMIN (SMK_MAXLEN + 2 * SMK_DIGITLEN) +#define SMK_CIPSOMIN (SMK_LABELLEN + 2 * SMK_DIGITLEN) +#define SMK_CIPSOMAX (SMK_CIPSOMIN + SMACK_CIPSO_MAXCATNUM * SMK_DIGITLEN) + +/* + * Values for parsing MAC rules + * SMK_ACCESS: Maximum possible combination of access permissions + * SMK_ACCESSLEN: Maximum length for a rule access field + * SMK_LOADLEN: Smack rule length + */ +#define SMK_ACCESS "rwxa" +#define SMK_ACCESSLEN (sizeof(SMK_ACCESS) - 1) +#define SMK_LOADLEN (SMK_LABELLEN + SMK_LABELLEN + SMK_ACCESSLEN) + /* * Seq_file read operations for /smack/load @@ -229,14 +242,10 @@ static void smk_set_access(struct smack_rule *srp) * The format is exactly: * char subject[SMK_LABELLEN] * char object[SMK_LABELLEN] - * char access[SMK_ACCESSKINDS] - * - * Anything following is commentary and ignored. + * char access[SMK_ACCESSLEN] * - * writes must be SMK_LABELLEN+SMK_LABELLEN+4 bytes. + * writes must be SMK_LABELLEN+SMK_LABELLEN+SMK_ACCESSLEN bytes. */ -#define MINIMUM_LOAD (SMK_LABELLEN + SMK_LABELLEN + SMK_ACCESSKINDS) - static ssize_t smk_write_load(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { @@ -253,7 +262,7 @@ static ssize_t smk_write_load(struct file *file, const char __user *buf, return -EPERM; if (*ppos != 0) return -EINVAL; - if (count < MINIMUM_LOAD) + if (count != SMK_LOADLEN) return -EINVAL; data = kzalloc(count, GFP_KERNEL); @@ -513,7 +522,7 @@ static ssize_t smk_write_cipso(struct file *file, const char __user *buf, return -EPERM; if (*ppos != 0) return -EINVAL; - if (count <= SMK_CIPSOMIN) + if (count < SMK_CIPSOMIN || count > SMK_CIPSOMAX) return -EINVAL; data = kzalloc(count + 1, GFP_KERNEL); @@ -547,7 +556,7 @@ static ssize_t smk_write_cipso(struct file *file, const char __user *buf, if (ret != 1 || catlen > SMACK_CIPSO_MAXCATNUM) goto out; - if (count <= (SMK_CIPSOMIN + catlen * SMK_DIGITLEN)) + if (count != (SMK_CIPSOMIN + catlen * SMK_DIGITLEN)) goto out; memset(mapcatset, 0, sizeof(mapcatset)); |