Messages in this thread Patch in this message | | | Date | Fri, 3 Aug 2018 11:36:04 +0200 | Subject | [PATCH] selinux: stricter parsing in mls_context_to_sid() | From | Jann Horn <> |
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mls_context_to_sid incorrectly accepted MLS context strings that are followed by a dash and trailing garbage.
Before this change, the following command works:
# mount -t tmpfs -o 'context=system_u:object_r:tmp_t:s0-s0:c0-BLAH' \ none mount
After this change, it fails with the following error message in dmesg:
SELinux: security_context_str_to_sid(system_u:object_r:tmp_t:s0-s0:c0-BLAH) failed for (dev tmpfs, type tmpfs) errno=-22
This is not an important bug; but it is a small quirk that was useful for exploiting a vulnerability in fusermount.
This patch does not change the behavior when the policy does not have MLS enabled.
Signed-off-by: Jann Horn <jannh@google.com> --- security/selinux/ss/mls.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/security/selinux/ss/mls.c b/security/selinux/ss/mls.c index 39475fb455bc..2c73d612d2ee 100644 --- a/security/selinux/ss/mls.c +++ b/security/selinux/ss/mls.c @@ -344,7 +344,7 @@ int mls_context_to_sid(struct policydb *pol, break; } } - if (delim == '-') { + if (delim == '-' && l == 0) { /* Extract high sensitivity. */ scontextp = p; while (*p && *p != ':') -- 2.18.0.597.ga71716f1ad-goog
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