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 2EF701DE2A5; Tue, 8 Oct 2024 13:06:01 +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=1728392762; cv=none; b=Pm7IteE+cmDuXiCuatoYRbibd+U92u6d2Ert0ek9uaAALr1ARM4CQaEkCU+Fi2iowGNbE/lulr6LIKuo0R7NPhc6zKlF6vXgKGSgb4QplNKbthuqxn6SsxGVZWhYXuXMK1h+Ky3YeP5trT5nPG2BTXJMGKU/7QDPe3yLPUXzL74= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728392762; c=relaxed/simple; bh=Z5TDdAQZ63xndN1moF2wjHlJvWZDVBaSH6hvdSu1Ow4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=htc9I1nCGK6O8cq6g/m2PKsSBi4J6VDNiyD0KFgi0QtSjFDeQSWO7SszVNG1K/rHVYHuJRQ3no/NF7oeB0ijAkWgaVgiJE7rS/Ze5eHzXK/Vy+TjXQJqKlExsf/NbXwifpviv4Bi5s8Gk15k5K654T8bFx31ogKE+SwYivd0sIs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Cphpgdxh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Cphpgdxh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 54F33C4CEC7; Tue, 8 Oct 2024 13:06:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1728392761; bh=Z5TDdAQZ63xndN1moF2wjHlJvWZDVBaSH6hvdSu1Ow4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CphpgdxhucxD3D4K0Th+akNhNgrkeCKBQ9INfMvXQl5TJki7vC9N/Sj/NOIyplkQd PlVA4BQ1QjOPtKURE0gGg4OmgXjedoyrSYXJP4xXAS8MVo2Dpzb7Iv4lE1+CxY1LBC LpRnzomnZbzDvh/r+nEzv8TA0cN53+u0gTruJWzQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Steve Sistare , David Hildenbrand , Jason Gunthorpe , Matthew Wilcox , Muchun Song , Peter Xu , Vivek Kasireddy , Andrew Morton Subject: [PATCH 6.11 480/558] mm/filemap: fix filemap_get_folios_contig THP panic Date: Tue, 8 Oct 2024 14:08:30 +0200 Message-ID: <20241008115721.126838926@linuxfoundation.org> X-Mailer: git-send-email 2.46.2 In-Reply-To: <20241008115702.214071228@linuxfoundation.org> References: <20241008115702.214071228@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.11-stable review patch. If anyone has any objections, please let me know. ------------------ From: Steve Sistare commit c225c4f6056b46a8a5bf2ed35abf17a2d6887691 upstream. Patch series "memfd-pin huge page fixes". Fix multiple bugs that occur when using memfd_pin_folios with hugetlb pages and THP. The hugetlb bugs only bite when the page is not yet faulted in when memfd_pin_folios is called. The THP bug bites when the starting offset passed to memfd_pin_folios is not huge page aligned. See the commit messages for details. This patch (of 5): memfd_pin_folios on memory backed by THP panics if the requested start offset is not huge page aligned: BUG: kernel NULL pointer dereference, address: 0000000000000036 RIP: 0010:filemap_get_folios_contig+0xdf/0x290 RSP: 0018:ffffc9002092fbe8 EFLAGS: 00010202 RAX: 0000000000000002 RBX: 0000000000000002 RCX: 0000000000000002 The fault occurs here, because xas_load returns a folio with value 2: filemap_get_folios_contig() for (folio = xas_load(&xas); folio && xas.xa_index <= end; folio = xas_next(&xas)) { ... if (!folio_try_get(folio)) <-- BOOM "2" is an xarray sibling entry. We get it because memfd_pin_folios does not round the indices passed to filemap_get_folios_contig to huge page boundaries for THP, so we load from the middle of a huge page range see a sibling. (It does round for hugetlbfs, at the is_file_hugepages test). To fix, if the folio is a sibling, then return the next index as the starting point for the next call to filemap_get_folios_contig. Link: https://lkml.kernel.org/r/1725373521-451395-1-git-send-email-steven.sistare@oracle.com Link: https://lkml.kernel.org/r/1725373521-451395-2-git-send-email-steven.sistare@oracle.com Fixes: 89c1905d9c14 ("mm/gup: introduce memfd_pin_folios() for pinning memfd folios") Signed-off-by: Steve Sistare Cc: David Hildenbrand Cc: Jason Gunthorpe Cc: Matthew Wilcox Cc: Muchun Song Cc: Peter Xu Cc: Vivek Kasireddy Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/filemap.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2181,6 +2181,10 @@ unsigned filemap_get_folios_contig(struc if (xa_is_value(folio)) goto update_start; + /* If we landed in the middle of a THP, continue at its end. */ + if (xa_is_sibling(folio)) + goto update_start; + if (!folio_try_get(folio)) goto retry;