From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F3F261B2193; Wed, 16 Oct 2024 21:56:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729115817; cv=none; b=eWg8MkEMU8R9sWp7KK0PzHXlXW2PKJhbfCJdjyqE50Y1g3qelB4f1FlPmPd3glXBfu9lmhoMqUQ2eqKrdiikGJmJb95hwaCdYAuyPWHRDkuwQUPPFCJ6yNUIwbv95ktlyIAO159GvfBqQsrMniNDYi0zg0FnQufBh3xBhpSUw5o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729115817; c=relaxed/simple; bh=imJM00J/kQiyZJ1Q7WwvmA2krbMI5+jzDnCnq2xgjWw=; h=Date:To:From:Subject:Message-Id; b=JsL5nhEVCVT5oSEIXDapKDnxBOAh257AKgFYeD784CtzGqKH6+gSh0lR5PQWSm5cfgAdB138Gf5OW87tIUw3F8cTyBKrnayLnuRYgLh36SKgiulPGu7/PrDvWzSZE/kYFCvrd9fpVtSo5IPI02DRgmdgsSErRRcJq3OESUuORcU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=QkOPXSi1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="QkOPXSi1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6EF61C4CEC7; Wed, 16 Oct 2024 21:56:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1729115816; bh=imJM00J/kQiyZJ1Q7WwvmA2krbMI5+jzDnCnq2xgjWw=; h=Date:To:From:Subject:From; b=QkOPXSi1i4L9W4GgMsW7F9uUL+A6Wc6duwR2sPZeW/uunP5UrQsCWkQOx4fRar6wn zraxAUDzsVd1AhazYxT+8PgldQ9vHUJkesPshWG6WswCsbtkPdtehTt02gf5pzf0Ju TwpKZucGxDkEdCzIn6vHwOMr3ehg4eDKFDBbZfIo= Date: Wed, 16 Oct 2024 14:56:55 -0700 To: mm-commits@vger.kernel.org,syoshida@redhat.com,stable@vger.kernel.org,pasha.tatashin@soleen.com,minchan@kernel.org,jgg@nvidia.com,david@redhat.com,apopple@nvidia.com,jhubbard@nvidia.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions.patch added to mm-hotfixes-unstable branch Message-Id: <20241016215656.6EF61C4CEC7@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/gup: stop leaking pinned pages in low memory conditions has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: John Hubbard Subject: mm/gup: stop leaking pinned pages in low memory conditions Date: Wed, 16 Oct 2024 13:22:42 -0700 If a driver tries to call any of the pin_user_pages*(FOLL_LONGTERM) family of functions, and requests "too many" pages, then the call will erroneously leave pages pinned. This is visible in user space as an actual memory leak. Repro is trivial: just make enough pin_user_pages(FOLL_LONGTERM) calls to exhaust memory. The root cause of the problem is this sequence, within __gup_longterm_locked(): __get_user_pages_locked() rc = check_and_migrate_movable_pages() ...which gets retried in a loop. The loop error handling is incomplete, clearly due to a somewhat unusual and complicated tri-state error API. But anyway, if -ENOMEM, or in fact, any unexpected error is returned from check_and_migrate_movable_pages(), then __gup_longterm_locked() happily returns the error, while leaving the pages pinned. In the failed case, which is an app that requests (via a device driver) 30720000000 bytes to be pinned, and then exits, I see this: $ grep foll /proc/vmstat nr_foll_pin_acquired 7502048 nr_foll_pin_released 2048 And after applying this patch, it returns to balanced pins: $ grep foll /proc/vmstat nr_foll_pin_acquired 7502048 nr_foll_pin_released 7502048 Fix this by unpinning the pages that __get_user_pages_locked() has pinned, in such error cases. Link: https://lkml.kernel.org/r/20241016202242.456953-1-jhubbard@nvidia.com Fixes: 24a95998e9ba ("mm/gup.c: simplify and fix check_and_migrate_movable_pages() return codes") Signed-off-by: John Hubbard Cc: Alistair Popple Cc: Shigeru Yoshida Cc: David Hildenbrand Cc: Jason Gunthorpe Cc: Minchan Kim Cc: Pasha Tatashin Cc: Signed-off-by: Andrew Morton --- mm/gup.c | 11 +++++++++++ 1 file changed, 11 insertions(+) --- a/mm/gup.c~mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions +++ a/mm/gup.c @@ -2492,6 +2492,17 @@ static long __gup_longterm_locked(struct /* FOLL_LONGTERM implies FOLL_PIN */ rc = check_and_migrate_movable_pages(nr_pinned_pages, pages); + + /* + * The __get_user_pages_locked() call happens before we know + * that whether it's possible to successfully complete the whole + * operation. To compensate for this, if we get an unexpected + * error (such as -ENOMEM) then we must unpin everything, before + * erroring out. + */ + if (rc != -EAGAIN && rc != 0) + unpin_user_pages(pages, nr_pinned_pages); + } while (rc == -EAGAIN); memalloc_pin_restore(flags); return rc ? rc : nr_pinned_pages; _ Patches currently in -mm which might be from jhubbard@nvidia.com are mm-gup-stop-leaking-pinned-pages-in-low-memory-conditions.patch kaslr-rename-physmem_end-and-physmem_end-to-direct_map_physmem_end.patch