kmalloc() can't always allocate large enough buffers for big_key to use for crypto (1MB + some metadata) so we cannot use that to allocate the buffer. Further, vmalloc'd pages can't be passed to sg_init_one() and the aead crypto accessors cannot be called progressively and must be passed all the data in one go (which means we can't pass the data in one block at a time).
Fix this by allocating the buffer pages individually and passing them through a multientry scatterlist to the crypto layer. This has the bonus advantage that we don't have to allocate a contiguous series of pages.
We then vmap() the page list and pass that through to the VFS read/write routines.
This can trigger a warning:
WARNING: CPU: 0 PID: 60912 at mm/page_alloc.c:3883 __alloc_pages_nodemask+0xb7c/0x15f8 ([<00000000002acbb6>] __alloc_pages_nodemask+0x1ee/0x15f8) [<00000000002dd356>] kmalloc_order+0x46/0x90 [<00000000002dd3e0>] kmalloc_order_trace+0x40/0x1f8 [<0000000000326a10>] __kmalloc+0x430/0x4c0 [<00000000004343e4>] big_key_preparse+0x7c/0x210 [<000000000042c040>] key_create_or_update+0x128/0x420 [<000000000042e52c>] SyS_add_key+0x124/0x220 [<00000000007bba2c>] system_call+0xc4/0x2b0
from the keyctl/padd/useradd test of the keyutils testsuite on s390x.
Note that it might be better to shovel data through in page-sized lumps instead as there's no particular need to use a monolithic buffer unless the kernel itself wants to access the data.
Fixes: 13100a72f40f ("Security: Keys: Big keys stored encrypted") Reported-by: Paul Bunyan pbunyan@redhat.com Signed-off-by: David Howells dhowells@redhat.com cc: Kirill Marinushkin k.marinushkin@gmail.com ---
security/keys/big_key.c | 110 +++++++++++++++++++++++++++++++++++++---------- 1 file changed, 87 insertions(+), 23 deletions(-)
diff --git a/security/keys/big_key.c b/security/keys/big_key.c index 929e14978c42..4e99e8ba8612 100644 --- a/security/keys/big_key.c +++ b/security/keys/big_key.c @@ -22,6 +22,13 @@ #include <keys/big_key-type.h> #include <crypto/aead.h>
+struct big_key_buf { + unsigned int nr_pages; + void *virt; + struct scatterlist *sg; + struct page *pages[]; +}; + /* * Layout of key payload words. */ @@ -91,10 +98,9 @@ static DEFINE_MUTEX(big_key_aead_lock); /* * Encrypt/decrypt big_key data */ -static int big_key_crypt(enum big_key_op op, u8 *data, size_t datalen, u8 *key) +static int big_key_crypt(enum big_key_op op, struct big_key_buf *buf, size_t datalen, u8 *key) { int ret; - struct scatterlist sgio; struct aead_request *aead_req; /* We always use a zero nonce. The reason we can get away with this is * because we're using a different randomly generated key for every @@ -109,8 +115,7 @@ static int big_key_crypt(enum big_key_op op, u8 *data, size_t datalen, u8 *key) return -ENOMEM;
memset(zero_nonce, 0, sizeof(zero_nonce)); - sg_init_one(&sgio, data, datalen + (op == BIG_KEY_ENC ? ENC_AUTHTAG_SIZE : 0)); - aead_request_set_crypt(aead_req, &sgio, &sgio, datalen, zero_nonce); + aead_request_set_crypt(aead_req, buf->sg, buf->sg, datalen, zero_nonce); aead_request_set_callback(aead_req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL); aead_request_set_ad(aead_req, 0);
@@ -130,21 +135,81 @@ static int big_key_crypt(enum big_key_op op, u8 *data, size_t datalen, u8 *key) }
/* + * Free up the buffer. + */ +static void big_key_free_buffer(struct big_key_buf *buf) +{ + unsigned int i; + + if (buf->virt) { + memset(buf->virt, 0, buf->nr_pages * PAGE_SIZE); + vunmap(buf->virt); + } + + for (i = 0; i < buf->nr_pages; i++) + if (buf->pages[i]) + __free_page(buf->pages[i]); + + kfree(buf); +} + +/* + * Allocate a buffer consisting of a set of pages with a virtual mapping + * applied over them. + */ +static void *big_key_alloc_buffer(size_t len) +{ + struct big_key_buf *buf; + unsigned int npg = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; + unsigned int i, l; + + buf = kzalloc(sizeof(struct big_key_buf) + + sizeof(struct page) * npg + + sizeof(struct scatterlist) * npg, + GFP_KERNEL); + if (!buf) + return NULL; + + buf->nr_pages = npg; + buf->sg = (void *)(buf->pages + npg); + sg_init_table(buf->sg, npg); + + for (i = 0; i < buf->nr_pages; i++) { + buf->pages[i] = alloc_page(GFP_KERNEL); + if (!buf->pages[i]) + goto nomem; + + l = min(len, PAGE_SIZE); + sg_set_page(&buf->sg[i], buf->pages[i], l, 0); + len -= l; + } + + buf->virt = vmap(buf->pages, buf->nr_pages, VM_MAP, PAGE_KERNEL); + if (!buf->virt) + goto nomem; + + return buf; + +nomem: + big_key_free_buffer(buf); + return NULL; +} + +/* * Preparse a big key */ int big_key_preparse(struct key_preparsed_payload *prep) { + struct big_key_buf *buf; struct path *path = (struct path *)&prep->payload.data[big_key_path]; struct file *file; u8 *enckey; - u8 *data = NULL; ssize_t written; - size_t datalen = prep->datalen; + size_t datalen = prep->datalen, enclen = datalen + ENC_AUTHTAG_SIZE; int ret;
- ret = -EINVAL; if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data) - goto error; + return -EINVAL;
/* Set an arbitrary quota */ prep->quotalen = 16; @@ -157,13 +222,12 @@ int big_key_preparse(struct key_preparsed_payload *prep) * * File content is stored encrypted with randomly generated key. */ - size_t enclen = datalen + ENC_AUTHTAG_SIZE; loff_t pos = 0;
- data = kmalloc(enclen, GFP_KERNEL); - if (!data) + buf = big_key_alloc_buffer(enclen); + if (!buf) return -ENOMEM; - memcpy(data, prep->data, datalen); + memcpy(buf->virt, prep->data, datalen);
/* generate random key */ enckey = kmalloc(ENC_KEY_SIZE, GFP_KERNEL); @@ -176,7 +240,7 @@ int big_key_preparse(struct key_preparsed_payload *prep) goto err_enckey;
/* encrypt aligned data */ - ret = big_key_crypt(BIG_KEY_ENC, data, datalen, enckey); + ret = big_key_crypt(BIG_KEY_ENC, buf, datalen, enckey); if (ret) goto err_enckey;
@@ -187,7 +251,7 @@ int big_key_preparse(struct key_preparsed_payload *prep) goto err_enckey; }
- written = kernel_write(file, data, enclen, &pos); + written = kernel_write(file, buf->virt, enclen, &pos); if (written != enclen) { ret = written; if (written >= 0) @@ -202,7 +266,7 @@ int big_key_preparse(struct key_preparsed_payload *prep) *path = file->f_path; path_get(path); fput(file); - kzfree(data); + big_key_free_buffer(buf); } else { /* Just store the data in a buffer */ void *data = kmalloc(datalen, GFP_KERNEL); @@ -220,7 +284,7 @@ int big_key_preparse(struct key_preparsed_payload *prep) err_enckey: kzfree(enckey); error: - kzfree(data); + big_key_free_buffer(buf); return ret; }
@@ -298,15 +362,15 @@ long big_key_read(const struct key *key, char __user *buffer, size_t buflen) return datalen;
if (datalen > BIG_KEY_FILE_THRESHOLD) { + struct big_key_buf *buf; struct path *path = (struct path *)&key->payload.data[big_key_path]; struct file *file; - u8 *data; u8 *enckey = (u8 *)key->payload.data[big_key_data]; size_t enclen = datalen + ENC_AUTHTAG_SIZE; loff_t pos = 0;
- data = kmalloc(enclen, GFP_KERNEL); - if (!data) + buf = big_key_alloc_buffer(enclen); + if (!buf) return -ENOMEM;
file = dentry_open(path, O_RDONLY, current_cred()); @@ -316,26 +380,26 @@ long big_key_read(const struct key *key, char __user *buffer, size_t buflen) }
/* read file to kernel and decrypt */ - ret = kernel_read(file, data, enclen, &pos); + ret = kernel_read(file, buf->virt, enclen, &pos); if (ret >= 0 && ret != enclen) { ret = -EIO; goto err_fput; }
- ret = big_key_crypt(BIG_KEY_DEC, data, enclen, enckey); + ret = big_key_crypt(BIG_KEY_DEC, buf, enclen, enckey); if (ret) goto err_fput;
ret = datalen;
/* copy decrypted data to user */ - if (copy_to_user(buffer, data, datalen) != 0) + if (copy_to_user(buffer, buf->virt, datalen) != 0) ret = -EFAULT;
err_fput: fput(file); error: - kzfree(data); + big_key_free_buffer(buf); } else { ret = datalen; if (copy_to_user(buffer, key->payload.data[big_key_data],