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ipc/shm.c: avoid ipc_rcu_putref for failed ipc_addid() 

Loosely based on a patch from Kees Cook <keescook@chromium.org>:
 - id and error can be merged
 - if operations before ipc_addid() fail, then use call_rcu() directly.

The difference is that call_rcu is used for failures after
security_shm_alloc(), to continue to guaranteed an rcu delay for
security_sem_free().

Link: http://lkml.kernel.org/r/20170525185107.12869-15-manfred@colorfullife.com
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Manfred Spraul 2017-07-12 14:35:16 -07:00 committed by Linus Torvalds
parent 2ec55f8024
commit a2642f8770
1 changed files with 3 additions and 6 deletions
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9
ipc/shm.c
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@ -548,7 +548,6 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
size_t numpages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
struct file *file;
char name[13];
int id;
vm_flags_t acctflag = 0;
if (size < SHMMIN || size > ns->shm_ctlmax)
@ -617,11 +616,9 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
shp->shm_file = file;
shp->shm_creator = current;
id = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni);
if (id < 0) {
error = id;
error = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni);
if (error < 0)
goto no_id;
}
list_add(&shp->shm_clist, &current->sysvshm.shm_clist);
@ -643,7 +640,7 @@ no_id:
user_shm_unlock(size, shp->mlock_user);
fput(file);
no_file:
ipc_rcu_putref(&shp->shm_perm, shm_rcu_free);
call_rcu(&shp->shm_perm.rcu, shm_rcu_free);
return error;
}