This is a note to let you know that I've just added the patch titled
aio: fix io_setup/io_destroy race
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
aio-fix-io_setup-io_destroy-race.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 86b62a2cb4fc09037bbce2959d2992962396fd7f Mon Sep 17 00:00:00 2001
From: Al Viro <[email protected]>
Date: Wed, 7 Mar 2012 05:16:35 +0000
Subject: aio: fix io_setup/io_destroy race
From: Al Viro <[email protected]>
commit 86b62a2cb4fc09037bbce2959d2992962396fd7f upstream.
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 <[email protected]>
Acked-by: Benjamin LaHaise <[email protected]>
Reviewed-by: Jeff Moyer <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
fs/aio.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -273,7 +273,7 @@ static struct kioctx *ioctx_alloc(unsign
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);
@@ -1256,10 +1256,10 @@ SYSCALL_DEFINE2(io_setup, unsigned, nr_e
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);
}
Patches currently in stable-queue which might be from [email protected]
are
queue-3.0/aio-fix-io_setup-io_destroy-race.patch
queue-3.0/aio-fix-the-too-late-munmap-race.patch
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