| Message ID | 20171026205744.105566-1-ebiggers3@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 2017-10-26 at 13:57 -0700, Eric Biggers wrote: > From: Eric Biggers <ebiggers@google.com> > > When calling keyctl_read() on a key of type "trusted", if the > user-supplied buffer was too small, the kernel ignored the buffer length > and just wrote past the end of the buffer, potentially corrupting > userspace memory. Fix it by instead returning the size required, as per > the documentation for keyctl_read(). > > We also don't even fill the buffer at all in this case, as this is > slightly easier to implement than doing a short read, and either > behavior appears to be permitted. It also makes it match the behavior > of the "encrypted" key type. > > Fixes: d00a1c72f7f4 ("keys: add new trusted key-type") > Reported-by: Ben Hutchings <ben@decadent.org.uk> > Cc: <stable@vger.kernel.org> # v2.6.38+ > Signed-off-by: Eric Biggers <ebiggers@google.com> Thanks! Reviewed-by: Mimi Zohar <zohar@linux.vnet.ibm.com> > --- > security/keys/trusted.c | 23 ++++++++++++----------- > 1 file changed, 12 insertions(+), 11 deletions(-) > > diff --git a/security/keys/trusted.c b/security/keys/trusted.c > index bd85315cbfeb..98aa89ff7bfd 100644 > --- a/security/keys/trusted.c > +++ b/security/keys/trusted.c > @@ -1147,20 +1147,21 @@ static long trusted_read(const struct key *key, char __user *buffer, > p = dereference_key_locked(key); > if (!p) > return -EINVAL; > - if (!buffer || buflen <= 0) > - return 2 * p->blob_len; > - ascii_buf = kmalloc(2 * p->blob_len, GFP_KERNEL); > - if (!ascii_buf) > - return -ENOMEM; > > - bufp = ascii_buf; > - for (i = 0; i < p->blob_len; i++) > - bufp = hex_byte_pack(bufp, p->blob[i]); > - if ((copy_to_user(buffer, ascii_buf, 2 * p->blob_len)) != 0) { > + if (buffer && buflen >= 2 * p->blob_len) { > + ascii_buf = kmalloc(2 * p->blob_len, GFP_KERNEL); > + if (!ascii_buf) > + return -ENOMEM; > + > + bufp = ascii_buf; > + for (i = 0; i < p->blob_len; i++) > + bufp = hex_byte_pack(bufp, p->blob[i]); > + if (copy_to_user(buffer, ascii_buf, 2 * p->blob_len) != 0) { > + kzfree(ascii_buf); > + return -EFAULT; > + } > kzfree(ascii_buf); > - return -EFAULT; > } > - kzfree(ascii_buf); > return 2 * p->blob_len; > } > -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, 26 Oct 2017, Eric Biggers wrote: > From: Eric Biggers <ebiggers@google.com> > > When calling keyctl_read() on a key of type "trusted", if the > user-supplied buffer was too small, the kernel ignored the buffer length > and just wrote past the end of the buffer, potentially corrupting > userspace memory. Fix it by instead returning the size required, as per > the documentation for keyctl_read(). > > We also don't even fill the buffer at all in this case, as this is > slightly easier to implement than doing a short read, and either > behavior appears to be permitted. It also makes it match the behavior > of the "encrypted" key type. > > Fixes: d00a1c72f7f4 ("keys: add new trusted key-type") > Reported-by: Ben Hutchings <ben@decadent.org.uk> > Cc: <stable@vger.kernel.org> # v2.6.38+ > Signed-off-by: Eric Biggers <ebiggers@google.com> Reviewed-by: James Morris <james.l.morris@oracle.com>
On Thu, 26 Oct 2017, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
David, this needs to go to Linus.
Are you planning on pushing out more fixes for this -rc or shuld I just
send it up via my tree?
diff --git a/security/keys/trusted.c b/security/keys/trusted.c index bd85315cbfeb..98aa89ff7bfd 100644 --- a/security/keys/trusted.c +++ b/security/keys/trusted.c @@ -1147,20 +1147,21 @@ static long trusted_read(const struct key *key, char __user *buffer, p = dereference_key_locked(key); if (!p) return -EINVAL; - if (!buffer || buflen <= 0) - return 2 * p->blob_len; - ascii_buf = kmalloc(2 * p->blob_len, GFP_KERNEL); - if (!ascii_buf) - return -ENOMEM; - bufp = ascii_buf; - for (i = 0; i < p->blob_len; i++) - bufp = hex_byte_pack(bufp, p->blob[i]); - if ((copy_to_user(buffer, ascii_buf, 2 * p->blob_len)) != 0) { + if (buffer && buflen >= 2 * p->blob_len) { + ascii_buf = kmalloc(2 * p->blob_len, GFP_KERNEL); + if (!ascii_buf) + return -ENOMEM; + + bufp = ascii_buf; + for (i = 0; i < p->blob_len; i++) + bufp = hex_byte_pack(bufp, p->blob[i]); + if (copy_to_user(buffer, ascii_buf, 2 * p->blob_len) != 0) { + kzfree(ascii_buf); + return -EFAULT; + } kzfree(ascii_buf); - return -EFAULT; } - kzfree(ascii_buf); return 2 * p->blob_len; }