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Diffstat (limited to 'security/keys')
-rw-r--r--security/keys/internal.h12
-rw-r--r--security/keys/keyctl.c58
2 files changed, 55 insertions, 15 deletions
diff --git a/security/keys/internal.h b/security/keys/internal.h
index ba3e2da14cef..6d0ca48ae9a5 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -16,6 +16,8 @@
#include <linux/keyctl.h>
#include <linux/refcount.h>
#include <linux/compat.h>
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
struct iovec;
@@ -349,4 +351,14 @@ static inline void key_check(const struct key *key)
#endif
+/*
+ * Helper function to clear and free a kvmalloc'ed memory object.
+ */
+static inline void __kvzfree(const void *addr, size_t len)
+{
+ if (addr) {
+ memset((void *)addr, 0, len);
+ kvfree(addr);
+ }
+}
#endif /* _INTERNAL_H */
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 434ed9defd3a..0062e422e0fd 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -339,7 +339,7 @@ long keyctl_update_key(key_serial_t id,
payload = NULL;
if (plen) {
ret = -ENOMEM;
- payload = kmalloc(plen, GFP_KERNEL);
+ payload = kvmalloc(plen, GFP_KERNEL);
if (!payload)
goto error;
@@ -360,7 +360,7 @@ long keyctl_update_key(key_serial_t id,
key_ref_put(key_ref);
error2:
- kzfree(payload);
+ __kvzfree(payload, plen);
error:
return ret;
}
@@ -827,7 +827,8 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
struct key *key;
key_ref_t key_ref;
long ret;
- char *key_data;
+ char *key_data = NULL;
+ size_t key_data_len;
/* find the key first */
key_ref = lookup_user_key(keyid, 0, 0);
@@ -878,24 +879,51 @@ can_read_key:
* Allocating a temporary buffer to hold the keys before
* transferring them to user buffer to avoid potential
* deadlock involving page fault and mmap_sem.
+ *
+ * key_data_len = (buflen <= PAGE_SIZE)
+ * ? buflen : actual length of key data
+ *
+ * This prevents allocating arbitrary large buffer which can
+ * be much larger than the actual key length. In the latter case,
+ * at least 2 passes of this loop is required.
*/
- key_data = kmalloc(buflen, GFP_KERNEL);
+ key_data_len = (buflen <= PAGE_SIZE) ? buflen : 0;
+ for (;;) {
+ if (key_data_len) {
+ key_data = kvmalloc(key_data_len, GFP_KERNEL);
+ if (!key_data) {
+ ret = -ENOMEM;
+ goto key_put_out;
+ }
+ }
- if (!key_data) {
- ret = -ENOMEM;
- goto key_put_out;
- }
- ret = __keyctl_read_key(key, key_data, buflen);
+ ret = __keyctl_read_key(key, key_data, key_data_len);
+
+ /*
+ * Read methods will just return the required length without
+ * any copying if the provided length isn't large enough.
+ */
+ if (ret <= 0 || ret > buflen)
+ break;
+
+ /*
+ * The key may change (unlikely) in between 2 consecutive
+ * __keyctl_read_key() calls. In this case, we reallocate
+ * a larger buffer and redo the key read when
+ * key_data_len < ret <= buflen.
+ */
+ if (ret > key_data_len) {
+ if (unlikely(key_data))
+ __kvzfree(key_data, key_data_len);
+ key_data_len = ret;
+ continue; /* Allocate buffer */
+ }
- /*
- * Read methods will just return the required length without
- * any copying if the provided length isn't large enough.
- */
- if (ret > 0 && ret <= buflen) {
if (copy_to_user(buffer, key_data, ret))
ret = -EFAULT;
+ break;
}
- kzfree(key_data);
+ __kvzfree(key_data, key_data_len);
key_put_out:
key_put(key);