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CVE request: kernel: Unused iocbs in a batch should not be accounted as active
From: Eugene Teo <eugene () redhat com>
Date: Wed, 18 Jan 2012 13:30:44 +0800

commit 69e4747ee9727d660b88d7e1efe0f4afcb35db1b
Author: Gleb Natapov <gleb () redhat com>
Date:   Sun Jan 8 17:07:28 2012 +0200

    Unused iocbs in a batch should not be accounted as active.

    Since commit 080d676de095 ("aio: allocate kiocbs in batches") iocbs
are allocated in a batch during processing of first iocbs.  All iocbs in
a batch are automatically added to ctx->active_reqs list and accounted
in ctx->reqs_active.

    If one (not the last one) of iocbs submitted by an user fails,
further iocbs are not processed, but they are still present in
ctx->active_reqs and accounted in ctx->reqs_active.  This causes process
to stuck in a D state in wait_for_all_aios() on exit since
ctx->reqs_active will never go down to zero.  Furthermore since
kiocb_batch_free() frees iocb without removing it from active_reqs list
the list become corrupted which may cause oops.

    Fix this by removing iocb from ctx->active_reqs and updating
ctx->reqs_active in kiocb_batch_free().

    Signed-off-by: Gleb Natapov <gleb () redhat com>
    Reviewed-by: Jeff Moyer <jmoyer () redhat com>
    Cc: stable () kernel org   # 3.2
    Signed-off-by: Linus Torvalds <torvalds () linux-foundation org>

Issue introduced in v3.2-rc1 via commit 080d676d.

Thanks, Eugene

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