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Date: Fri, 16 Mar 2012 16:34:49 -0700 From: Greg KH <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org Cc: torvalds@...ux-foundation.org, akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk, Al Viro <viro@...iv.linux.org.uk>, Benjamin LaHaise <bcrl@...ck.org>, Jeff Moyer <jmoyer@...hat.com> Subject: [ 02/38] aio: fix io_setup/io_destroy race 3.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Al Viro <viro@...IV.linux.org.uk> 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 <viro@...iv.linux.org.uk> Acked-by: Benjamin LaHaise <bcrl@...ck.org> Reviewed-by: Jeff Moyer <jmoyer@...hat.com> Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- 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); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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