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authorAl Viro <viro@ZenIV.linux.org.uk>2012-03-07 05:16:35 +0000
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-09 18:59:59 -0800
commit86b62a2cb4fc09037bbce2959d2992962396fd7f (patch)
treeea45bb1de1f49862415b5643dea840318d02ee67 /fs/aio.c
parent86e06008338e5712603613a0f6770500f79e83bd (diff)
downloadlinux-stericsson-86b62a2cb4fc09037bbce2959d2992962396fd7f.tar.gz
aio: fix io_setup/io_destroy race
Have ioctx_alloc() return an extra reference, so that caller would drop it on success and not bother with re-grabbing it on failure exit. The current code is obviously broken - io_destroy() from another thread that managed to guess the address io_setup() would've returned would free ioctx right under us; gets especially interesting if aio_context_t * we pass to io_setup() points to PROT_READ mapping, so put_user() fails and we end up doing io_destroy() on kioctx another thread has just got freed... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Acked-by: Benjamin LaHaise <bcrl@kvack.org> Reviewed-by: Jeff Moyer <jmoyer@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/aio.c')
-rw-r--r--fs/aio.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/aio.c b/fs/aio.c
index 67e4b9047cc9..f6578cb22d00 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -273,7 +273,7 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
mm = ctx->mm = current->mm;
atomic_inc(&mm->mm_count);
- atomic_set(&ctx->users, 1);
+ atomic_set(&ctx->users, 2);
spin_lock_init(&ctx->ctx_lock);
spin_lock_init(&ctx->ring_info.ring_lock);
init_waitqueue_head(&ctx->wait);
@@ -1338,10 +1338,10 @@ SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
ret = PTR_ERR(ioctx);
if (!IS_ERR(ioctx)) {
ret = put_user(ioctx->user_id, ctxp);
- if (!ret)
+ if (!ret) {
+ put_ioctx(ioctx);
return 0;
-
- get_ioctx(ioctx); /* io_destroy() expects us to hold a ref */
+ }
io_destroy(ioctx);
}