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authorEric Biggers <ebiggers@google.com>2017-11-02 00:47:03 +0000
committerJames Morris <james.l.morris@oracle.com>2017-11-02 20:58:05 +1100
commit3239b6f29bdfb4b0a2ba59df995fc9e6f4df7f1f (patch)
treeaaca6a6994664d8c704b49fd3cc7f995e75007a8
parent3a99df9a3d14cd866b5516f8cba515a3bfd554ab (diff)
KEYS: return full count in keyring_read() if buffer is too small
Commit e645016abc80 ("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: e645016abc80 ("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>
-rw-r--r--security/keys/keyring.c39
1 files changed, 19 insertions, 20 deletions
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index a7e51f793867..36f842ec87f0 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -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 */
- ctx.buffer = (key_serial_t __user *)buffer;
- ctx.buflen = buflen;
- ctx.count = 0;
- ret = assoc_array_iterate(&keyring->keys, keyring_read_iterator, &ctx);
- if (ret < 0) {
- kleave(" = %d [iterate]", ret);
- return ret;
+ /* 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);
+ if (ret < 0) {
+ 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;
}
/*