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Commit c2c737a0461e61a34676bd0bd1bc1a70a1b4e396

Authored by Davidlohr Bueso
Committed by Linus Torvalds
1 parent f42569b138
Exists in smarc-imx_3.14.28_1.0.0_ga and in 1 other branch imx_3.14.28_1.0.0_ga

ipc,shm: shorten critical region for shmat 

Similar to other system calls, acquire the kern_ipc_perm lock after doing
the initial permission and security checks.

[sasha.levin@oracle.com: dont leave do_shmat with rcu lock held]
Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 1 changed file with 10 additions and 4 deletions Side-by-side Diff

... ... @@ -19,6 +19,9 @@
19 19 * namespaces support
20 20 * OpenVZ, SWsoft Inc.
21 21 * Pavel Emelianov <xemul@openvz.org>
  22 + *
  23 + * Better ipc lock (kern_ipc_perm.lock) handling
  24 + * Davidlohr Bueso <davidlohr.bueso@hp.com>, June 2013.
22 25 */
23 26  
24 27 #include <linux/slab.h>
25 28  
... ... @@ -1086,10 +1089,11 @@
1086 1089 * additional creator id...
1087 1090 */
1088 1091 ns = current->nsproxy->ipc_ns;
1089   - shp = shm_lock_check(ns, shmid);
  1092 + rcu_read_lock();
  1093 + shp = shm_obtain_object_check(ns, shmid);
1090 1094 if (IS_ERR(shp)) {
1091 1095 err = PTR_ERR(shp);
1092   - goto out;
  1096 + goto out_unlock;
1093 1097 }
1094 1098  
1095 1099 err = -EACCES;
1096 1100  
... ... @@ -1100,11 +1104,13 @@
1100 1104 if (err)
1101 1105 goto out_unlock;
1102 1106  
  1107 + ipc_lock_object(&shp->shm_perm);
1103 1108 path = shp->shm_file->f_path;
1104 1109 path_get(&path);
1105 1110 shp->shm_nattch++;
1106 1111 size = i_size_read(path.dentry->d_inode);
1107   - shm_unlock(shp);
  1112 + ipc_unlock_object(&shp->shm_perm);
  1113 + rcu_read_unlock();
1108 1114  
1109 1115 err = -ENOMEM;
1110 1116 sfd = kzalloc(sizeof(*sfd), GFP_KERNEL);
... ... @@ -1175,7 +1181,7 @@
1175 1181 return err;
1176 1182  
1177 1183 out_unlock:
1178   - shm_unlock(shp);
  1184 + rcu_read_unlock();
1179 1185 out:
1180 1186 return err;
1181 1187 }