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 73AB83563D4; Fri, 24 Apr 2026 13:44:16 +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=1777038256; cv=none; b=DI4+bhMHLYMzCoADhwQx8sqLicvHArhMyakElNyat25Wx50TAa0oUUvzaQIHmy4WrUih2sGf25P43Tr3NYki0mjilSXHJZs+F0iSYvMpAB11htTl7OhxW061+OL9egqBQJEmRdawg0cp9AR99g0YXv/GwQMeNFWh6Wk56gXFfSY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777038256; c=relaxed/simple; bh=9R5O816f6x+Or8uvSMdrabubzuW0eXNuRVtRpMYirTE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=pS25rdbVT4uc8O+OdJuc2xnJwt6QwS5SCUxg7dLLZuH/skUvbCHKFDZzWspSr2pjg9duoCc5pZyTkkaJe36hpWO8zJXmSLVGiHqvUXss0WRd7PQRMbXi4YgzmLzQBIL69QASPxXbcPRVd01znSfqP3L1DU1JSHqT9syeNe8QCiQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=D8OS8IC6; 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="D8OS8IC6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0A105C19425; Fri, 24 Apr 2026 13:44:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1777038256; bh=9R5O816f6x+Or8uvSMdrabubzuW0eXNuRVtRpMYirTE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=D8OS8IC6bI75HX00FzyKCqVk8i2wzl3uFZcAN5LkyXua/7HjX0Mcw4Y/XA3VUk/5e otCagRBX6dMUqTcwRCI0JQ4DK1iIdbtFfidS3zwnD9MKP4CnsIe1skbUN7ZjzHSXD3 LG/r1qgwXXC+2+WrtBVuD2UNOvbOVPSZrHIhGBhc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, George Saad , Chao Yu , Jaegeuk Kim Subject: [PATCH 6.12 28/35] f2fs: fix use-after-free of sbi in f2fs_compress_write_end_io() Date: Fri, 24 Apr 2026 15:31:35 +0200 Message-ID: <20260424132417.663058811@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260424132411.427029259@linuxfoundation.org> References: <20260424132411.427029259@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore 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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: George Saad commit 39d4ee19c1e7d753dd655aebee632271b171f43a upstream. 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 Signed-off-by: Greg Kroah-Hartman --- fs/f2fs/compress.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) --- a/fs/f2fs/compress.c +++ b/fs/f2fs/compress.c @@ -1472,10 +1472,10 @@ void f2fs_compress_write_end_io(struct b 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]); @@ -1485,6 +1485,14 @@ void f2fs_compress_write_end_io(struct b 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,