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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 2/4] assoc_array: Fix shortcut creation From: David Howells To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, keyrings@vger.kernel.org, dhowells@redhat.com, ebiggers@kernel.org, linux-kernel@vger.kernel.org Date: Thu, 14 Feb 2019 16:20:15 +0000 Message-ID: <155016121107.8115.8131805004120069255.stgit@warthog.procyon.org.uk> In-Reply-To: <155016118572.8115.3243711127043478822.stgit@warthog.procyon.org.uk> References: <155016118572.8115.3243711127043478822.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 14 Feb 2019 16:20:17 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Fix the creation of shortcuts for which the length of the index key value is an exact multiple of the machine word size. The problem is that the code that blanks off the unused bits of the shortcut value malfunctions if the number of bits in the last word equals machine word size. This is due to the "<<" operator being given a shift of zero in this case, and so the mask that should be all zeros is all ones instead. This causes the subsequent masking operation to clear everything rather than clearing nothing. Ordinarily, the presence of the hash at the beginning of the tree index key makes the issue very hard to test for, but in this case, it was encountered due to a development mistake that caused the hash output to be either 0 (keyring) or 1 (non-keyring) only. This made it susceptible to the keyctl/unlink/valid test in the keyutils package. The fix is simply to skip the blanking if the shift would be 0. For example, an index key that is 64 bits long would produce a 0 shift and thus a 'blank' of all 1s. This would then be inverted and AND'd onto the index_key, incorrectly clearing the entire last word. Fixes: 3cb989501c26 ("Add a generic associative array implementation.") Signed-off-by: David Howells --- lib/assoc_array.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/lib/assoc_array.c b/lib/assoc_array.c index c6659cb37033..59875eb278ea 100644 --- a/lib/assoc_array.c +++ b/lib/assoc_array.c @@ -768,9 +768,11 @@ static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit, new_s0->index_key[i] = ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE); - blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK); - pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank); - new_s0->index_key[keylen - 1] &= ~blank; + if (level & ASSOC_ARRAY_KEY_CHUNK_MASK) { + blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK); + pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank); + new_s0->index_key[keylen - 1] &= ~blank; + } /* This now reduces to a node splitting exercise for which we'll need * to regenerate the disparity table.