KEYS: return full count in keyring_read() if buffer is too small (3239b6f2) · Commits · 戴 / test

Commit ("KEYS: fix writing past end of user-supplied buffer in keyring_read()") made keyring_read() stop corrupting userspace memory when the user-supplied buffer is too small. However it also made the return value in that case be the short buffer size rather than the size required, yet keyctl_read() is actually documented to return the size required. Therefore, switch it over to the documented behavior. Note that for now we continue to have it fill the short buffer, since it did that before (pre-v3.13) and dump_key_tree_aux() in keyutils arguably relies on it. Fixes: ("KEYS: fix writing past end of user-supplied buffer in keyring_read()") Reported-by:

Ben Hutchings <ben@decadent.org.uk> Cc: <stable@vger.kernel.org> # v3.13+ Signed-off-by:

Eric Biggers <ebiggers@google.com> Signed-off-by:

David Howells <dhowells@redhat.com> Reviewed-by:

James Morris <james.l.morris@oracle.com> Signed-off-by:

James Morris <james.l.morris@oracle.com>

security/keys/keyring.c

+19 −20

Original line number	Diff line number	Diff line
		@@ -459,34 +459,33 @@ static long keyring_read(const struct key *keyring,
		char __user *buffer, size_t buflen)
		{
		struct keyring_read_iterator_context ctx;
		unsigned long nr_keys;
		int ret;
		long ret;

		kenter("{%d},,%zu", key_serial(keyring), buflen);

		if (buflen & (sizeof(key_serial_t) - 1))
		return -EINVAL;

		nr_keys = keyring->keys.nr_leaves_on_tree;
		if (nr_keys == 0)
		return 0;

		/* Calculate how much data we could return */
		if (!buffer \|\| !buflen)
		return nr_keys * sizeof(key_serial_t);

		/* Copy the IDs of the subscribed keys into the buffer */
		/* Copy as many key IDs as fit into the buffer */
		if (buffer && buflen) {
		ctx.buffer = (key_serial_t __user *)buffer;
		ctx.buflen = buflen;
		ctx.count = 0;
		ret = assoc_array_iterate(&keyring->keys, keyring_read_iterator, &ctx);
		ret = assoc_array_iterate(&keyring->keys,
		keyring_read_iterator, &ctx);
		if (ret < 0) {
		kleave(" = %d [iterate]", ret);
		kleave(" = %ld [iterate]", ret);
		return ret;
		}
		}

		kleave(" = %zu [ok]", ctx.count);
		return ctx.count;
		/* Return the size of the buffer needed */
		ret = keyring->keys.nr_leaves_on_tree * sizeof(key_serial_t);
		if (ret <= buflen)
		kleave("= %ld [ok]", ret);
		else
		kleave("= %ld [buffer too small]", ret);
		return ret;
		}

		/*

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