[Devel] [PATCH rh7] keys, user: Fix high order allocation in user_instantiate()

[Andrey Ryabinin]

Adding user key might trigger 4-order allocation which is unreliable
in case of fragmented memory:

 ------------[ cut here ]------------
 WARNING: CPU: 3 PID: 134927 at mm/page_alloc.c:3533 __alloc_pages_nodemask+0x1b1/0x600
 order 4 >= 3, gfp 0x40d0
 Kernel panic - not syncing: panic_on_warn set ...
 CPU: 3 PID: 134927 Comm: add_key01 ve: 0 Kdump: loaded Tainted: G           OE  ------------   3.10.0-1127.18.2.vz7.163.15 #1 163.15
 Hardware name: Virtuozzo KVM, BIOS 1.11.0-2.vz7.2 04/01/2014
 Call Trace:
  dump_stack+0x19/0x1b
  panic+0xe8/0x21f
  __warn+0xfa/0x100
  warn_slowpath_fmt+0x5f/0x80
  __alloc_pages_nodemask+0x1b1/0x600
  alloc_pages_current+0x98/0x110
  kmalloc_order+0x18/0x40
  kmalloc_order_trace+0x26/0xa0
  __kmalloc+0x281/0x2a0
  user_instantiate+0x47/0x90
  __key_instantiate_and_link+0x54/0x100
  key_create_or_update+0x398/0x490
  SyS_add_key+0x12c/0x220
  system_call_fastpath+0x25/0x2a

Use kvmalloc() to avoid potential -ENOMEM due to fragmentation.

https://jira.sw.ru/browse/PSBM-107794
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 security/keys/user_defined.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c
index bc8d3227dc4b..b13d70b69069 100644
--- a/security/keys/user_defined.c
+++ b/security/keys/user_defined.c
@@ -9,6 +9,7 @@
  * 2 of the License, or (at your option) any later version.
  */
 
+#include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
@@ -75,7 +76,7 @@ int user_instantiate(struct key *key, struct key_preparsed_payload *prep)
 		goto error;
 
 	ret = -ENOMEM;
-	upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
+	upayload = kvmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 	if (!upayload)
 		goto error;
 
@@ -96,7 +97,8 @@ static void user_free_payload_rcu(struct rcu_head *head)
 	struct user_key_payload *payload;
 
 	payload = container_of(head, struct user_key_payload, rcu);
-	kzfree(payload);
+	memset(payload, 0, sizeof(*payload) + payload->datalen);
+	kvfree(payload);
 }
 
 /*
@@ -115,7 +117,7 @@ int user_update(struct key *key, struct key_preparsed_payload *prep)
 
 	/* construct a replacement payload */
 	ret = -ENOMEM;
-	upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
+	upayload = kvmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
 	if (!upayload)
 		goto error;
 
@@ -182,7 +184,8 @@ void user_destroy(struct key *key)
 {
 	struct user_key_payload *upayload = key->payload.data;
 
-	kzfree(upayload);
+	memset(upayload, 0, sizeof(*upayload) + upayload->datalen);
+	kvfree(upayload);
 }
 
 EXPORT_SYMBOL_GPL(user_destroy);
-- 
2.26.2