diff options
| author | Eric Biggers <ebiggers@google.com> | 2017-09-18 11:36:45 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-10-03 13:42:12 +0200 |
| commit | d4915c0ac29f1f511d857719e3f1f888802399c5 (patch) | |
| tree | 86d0a35eb34dd0dcae30ef3cdd97aa159724ef81 | |
| parent | 2dc6844f114d4579f121a0431eddd28904020457 (diff) | |
KEYS: fix writing past end of user-supplied buffer in keyring_read()
commit e645016abc803dafc75e4b8f6e4118f088900ffb upstream.
Userspace can call keyctl_read() on a keyring to get the list of IDs of
keys in the keyring. But if the user-supplied buffer is too small, the
kernel would write the full list anyway --- which will corrupt whatever
userspace memory happened to be past the end of the buffer. Fix it by
only filling the space that is available.
Fixes: b2a4df200d57 ("KEYS: Expand the capacity of a keyring")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | security/keys/keyring.c | 14 |
1 files changed, 5 insertions, 9 deletions
diff --git a/security/keys/keyring.c b/security/keys/keyring.c index f931ccfeefb0..262ed2a6b360 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -416,7 +416,7 @@ static void keyring_describe(const struct key *keyring, struct seq_file *m) } struct keyring_read_iterator_context { - size_t qty; + size_t buflen; size_t count; key_serial_t __user *buffer; }; @@ -428,9 +428,9 @@ static int keyring_read_iterator(const void *object, void *data) int ret; kenter("{%s,%d},,{%zu/%zu}", - key->type->name, key->serial, ctx->count, ctx->qty); + key->type->name, key->serial, ctx->count, ctx->buflen); - if (ctx->count >= ctx->qty) + if (ctx->count >= ctx->buflen) return 1; ret = put_user(key->serial, ctx->buffer); @@ -465,16 +465,12 @@ static long keyring_read(const struct key *keyring, return 0; /* Calculate how much data we could return */ - ctx.qty = nr_keys * sizeof(key_serial_t); - if (!buffer || !buflen) - return ctx.qty; - - if (buflen > ctx.qty) - ctx.qty = 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) { |