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 B07F730DECB for ; Fri, 24 Apr 2026 09:45:04 +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=1777023904; cv=none; b=kkaCf3F0WENo6drJCrYG0IB/jekFOcPi/wYlWA3OclYaSmucnmxLaSniq3rnTpoyGxToaJ9dA/1CY3kKQY7HZuWMZ72zi5hYtOq6aU2DLNICnq/bgO9oxtGFot73IMB1dsh9kAA1lwmBiM2n8BqR4IIxB22E3gStg/x3EnuaGDg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777023904; c=relaxed/simple; bh=HpHmXk5yx5RJU6Gksf/CT6BWv+nqQzf7v123H8kM+ww=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=VFlYVVtVj+vf/uWJkcv3cR7hH9sdAMg1YttETM4lLQpBip6ZQMOlEb86GdDfYCuNxTWTRycMWbVH0J1Dd93wnjOqZpXfuwXi3VSBMIajd02Cfwi8KHVUOcpo6yRJIcZzpK3rGyk7NCRGycKPw52tWCaDn8s1orNBOJt4/rpiOCs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=mePPlrYA; 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="mePPlrYA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED66FC19425; Fri, 24 Apr 2026 09:45:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1777023904; bh=HpHmXk5yx5RJU6Gksf/CT6BWv+nqQzf7v123H8kM+ww=; h=Subject:To:Cc:From:Date:From; b=mePPlrYAhPxxcPpoT1cAUKVSY4DLWOHb/T2rBmyPEGVhNxv+wT3dJ35TT5CARM/vL m5fd6X+7GUOP+YeXbweEqPec1YnEt/4KP4oLThBazS8OlfepKX08uuh+I7wLTjVhL4 4lODh+Tz9TQbExcxYRuzTd9tllAQtlk+RSMNe5Ro= Subject: FAILED: patch "[PATCH] f2fs: fix use-after-free of sbi in" failed to apply to 5.15-stable tree To: geoo115@gmail.com,chao@kernel.org,jaegeuk@kernel.org Cc: From: Date: Fri, 24 Apr 2026 11:45:01 +0200 Message-ID: <2026042401-wife-alkalize-08f3@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 39d4ee19c1e7d753dd655aebee632271b171f43a # git commit -s git send-email --to '' --in-reply-to '2026042401-wife-alkalize-08f3@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 39d4ee19c1e7d753dd655aebee632271b171f43a Mon Sep 17 00:00:00 2001 From: George Saad Date: Mon, 23 Mar 2026 11:21:23 +0000 Subject: [PATCH] f2fs: fix use-after-free of sbi in f2fs_compress_write_end_io() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In f2fs_compress_write_end_io(), dec_page_count(sbi, type) can bring the F2FS_WB_CP_DATA counter to zero, unblocking f2fs_wait_on_all_pages() in f2fs_put_super() on a concurrent unmount CPU. The unmount path then proceeds to call f2fs_destroy_page_array_cache(sbi), which destroys sbi->page_array_slab via kmem_cache_destroy(), and eventually kfree(sbi). Meanwhile, the bio completion callback is still executing: when it reaches page_array_free(sbi, ...), it dereferences sbi->page_array_slab — a destroyed slab cache — to call kmem_cache_free(), causing a use-after-free. This is the same class of bug as CVE-2026-23234 (which fixed the equivalent race in f2fs_write_end_io() in data.c), but in the compressed writeback completion path that was not covered by that fix. Fix this by moving dec_page_count() to after page_array_free(), so that all sbi accesses complete before the counter decrement that can unblock unmount. For non-last folios (where atomic_dec_return on cic->pending_pages is nonzero), dec_page_count is called immediately before returning — page_array_free is not reached on this path, so there is no post-decrement sbi access. For the last folio, page_array_free runs while the F2FS_WB_CP_DATA counter is still nonzero (this folio has not yet decremented it), keeping sbi alive, and dec_page_count runs as the final operation. Fixes: 4c8ff7095bef ("f2fs: support data compression") Cc: stable@vger.kernel.org Signed-off-by: George Saad Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c index 8c76400ba631..aa8ba4cdfe34 100644 --- a/fs/f2fs/compress.c +++ b/fs/f2fs/compress.c @@ -1491,10 +1491,10 @@ void f2fs_compress_write_end_io(struct bio *bio, struct folio *folio) f2fs_compress_free_page(page); - dec_page_count(sbi, type); - - if (atomic_dec_return(&cic->pending_pages)) + if (atomic_dec_return(&cic->pending_pages)) { + dec_page_count(sbi, type); return; + } for (i = 0; i < cic->nr_rpages; i++) { WARN_ON(!cic->rpages[i]); @@ -1504,6 +1504,14 @@ void f2fs_compress_write_end_io(struct bio *bio, struct folio *folio) page_array_free(sbi, cic->rpages, cic->nr_rpages); kmem_cache_free(cic_entry_slab, cic); + + /* + * Make sure dec_page_count() is the last access to sbi. + * Once it drops the F2FS_WB_CP_DATA counter to zero, the + * unmount thread can proceed to destroy sbi and + * sbi->page_array_slab. + */ + dec_page_count(sbi, type); } static int f2fs_write_raw_pages(struct compress_ctx *cc,