Messages in this thread | | | Date | Wed, 19 May 2021 18:32:28 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH v12 1/8] arm64: mte: Handle race when synchronising tags |
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On Mon, May 17, 2021 at 01:32:32PM +0100, Steven Price wrote: > mte_sync_tags() used test_and_set_bit() to set the PG_mte_tagged flag > before restoring/zeroing the MTE tags. However if another thread were to > race and attempt to sync the tags on the same page before the first > thread had completed restoring/zeroing then it would see the flag is > already set and continue without waiting. This would potentially expose > the previous contents of the tags to user space, and cause any updates > that user space makes before the restoring/zeroing has completed to > potentially be lost. > > Since this code is run from atomic contexts we can't just lock the page > during the process. Instead implement a new (global) spinlock to protect > the mte_sync_page_tags() function. > > Fixes: 34bfeea4a9e9 ("arm64: mte: Clear the tags when a page is mapped in user-space with PROT_MTE") > Signed-off-by: Steven Price <steven.price@arm.com>
Other than the missing spinlock initialisation, the patch looks fine to me.
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
(though I'll probably queue it as a fix, waiting a couple of days for comments)
-- Catalin
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