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authorEric Biggers <ebiggers@google.com>2017-09-18 11:36:45 -0700
committerDavid Howells <dhowells@redhat.com>2017-09-25 15:19:57 +0100
commite645016abc803dafc75e4b8f6e4118f088900ffb (patch)
tree93714c8259d9bb33ae016a8dcf9239e77af00d81
parent7fc0786d956d9e59b68d282be9b156179846ea3d (diff)
downloadlinux-e645016abc803dafc75e4b8f6e4118f088900ffb.tar.bz2
KEYS: fix writing past end of user-supplied buffer in keyring_read()
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") Cc: <stable@vger.kernel.org> [v3.13+] Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: David Howells <dhowells@redhat.com>
-rw-r--r--security/keys/keyring.c14
1 files changed, 5 insertions, 9 deletions
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index de81793f9920..94f038967c17 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -423,7 +423,7 @@ 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;
};
@@ -435,9 +435,9 @@ 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);
@@ -472,16 +472,12 @@ 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) {