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65 lines
2.4 KiB
65 lines
2.4 KiB
From: John Johansen <john.johansen@canonical.com>
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Date: Tue, 20 Jul 2010 06:57:08 -0700
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Subject: AppArmor: Allow dfa backward compatibility with broken userspace
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Patch-mainline: 2.6.37?
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The apparmor_parser when compiling policy could generate invalid dfas
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that did not have sufficient padding to avoid invalid references, when
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used by the kernel. The kernels check to verify the next/check table
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size was broken meaning invalid dfas were being created by userspace
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and not caught.
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To remain compatible with old tools that are not fixed, pad the loaded
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dfas next/check table. The dfa's themselves are valid except for the
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high padding for potentially invalid transitions (high bounds error),
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which have a maximimum is 256 entries. So just allocate an extra null filled
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256 entries for the next/check tables. This will guarentee all bounds
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are good and invalid transitions go to the null (0) state.
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Signed-off-by: John Johansen <john.johansen@canonical.com>
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Acked-by: Jeff Mahoney <jeffm@suse.com>
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---
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security/apparmor/match.c | 17 +++++++++++++++++
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1 file changed, 17 insertions(+)
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--- a/security/apparmor/match.c
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+++ b/security/apparmor/match.c
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@@ -57,8 +57,17 @@ static struct table_header *unpack_table
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if (bsize < tsize)
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goto out;
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+ /* Pad table allocation for next/check by 256 entries to remain
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+ * backwards compatible with old (buggy) tools and remain safe without
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+ * run time checks
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+ */
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+ if (th.td_id == YYTD_ID_NXT || th.td_id == YYTD_ID_CHK)
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+ tsize += 256 * th.td_flags;
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+
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table = kvmalloc(tsize);
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if (table) {
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+ /* ensure the pad is clear, else there will be errors */
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+ memset(table, 0, tsize);
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*table = th;
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if (th.td_flags == YYTD_DATA8)
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UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
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@@ -134,11 +143,19 @@ static int verify_dfa(struct aa_dfa *dfa
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goto out;
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if (flags & DFA_FLAG_VERIFY_STATES) {
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+ int warning = 0;
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for (i = 0; i < state_count; i++) {
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if (DEFAULT_TABLE(dfa)[i] >= state_count)
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goto out;
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/* TODO: do check that DEF state recursion terminates */
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if (BASE_TABLE(dfa)[i] + 255 >= trans_count) {
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+ if (warning)
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+ continue;
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+ printk(KERN_WARNING "AppArmor DFA next/check "
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+ "upper bounds error fixed, upgrade "
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+ "user space tools \n");
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+ warning = 1;
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+ } else if (BASE_TABLE(dfa)[i] >= trans_count) {
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printk(KERN_ERR "AppArmor DFA next/check upper "
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"bounds error\n");
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goto out;
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