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 D784B3CDBA5; Thu, 24 Sep 2026 14:34:17 +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=1790260457; cv=none; b=P/DcQsJwntRSFkY1dbULxeLaUimWwtl2xq98mHAc7OgXoX/nh6Zwci8jMtM43lJGGvcJD3/wlxVkc8Tf1lWeak79E1zIwbUg5PWxRbu6tVoE5zsoWzWARN4EkQgZHA1KCKBCf+Yu+ZBviftfZrPfFqyIv13LNR8vihpyAhprW34= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790260457; c=relaxed/simple; bh=I5CKmhNtTnWeuzjiQtc94qyADu0YXow+af+CzKqUVMc=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=ubYu5DXF2bJxRHkviZeqewV34Bw8Bmz04NS9iYeR6vgWdxYhvuq3TbTphXkmPh5Sd4eUasNrYgdo5rb8hy8uWAbETe01ITNv9iFzo3FzT+aTQYQqAq3ShU5HZPGY+P62mrgU4qhNvHr/DIYjOv6I+rcOOVWPI7JWvnzFSNWYkzc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VIxTUZ7n; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VIxTUZ7n" Received: by smtp.kernel.org (Postfix) with ESMTPS id 82CACC2BCFB; Thu, 24 Sep 2026 14:34:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1790260457; bh=I5CKmhNtTnWeuzjiQtc94qyADu0YXow+af+CzKqUVMc=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=VIxTUZ7n+tsQy9idj+xDRS/iIX7BhWS7ODavv9m8cfbQY6cKNsLXwly9Xrns11vwc oB7D/Ixn1uJIsM4/So4VOazmOYPlus9+w/lYIElX6VjrzUVjkzMMaPxF2mBwRf1Pkj heZT1BgNiKJC+nxFnV95XFWXH0lN7pcH7Ih+o2XMcb7WGpmAJrwuaLGJuK/jvtqkpf 0qUIbBtxR2VtEQnDZtHu9i+eIeudTj3+HOx/GVKlxZxkXzgAA1xSwK92EEKCuh+rKW MIygV1Llhwv6+9ErppQ127L7zuCBQgDUJt3g5G5NnzNbfeadM6I5xV1b4bGXXednJ1 TUzVK2j64z+dw== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6126CC98321; Thu, 24 Sep 2026 14:34:17 +0000 (UTC) From: Joel Granados Date: Thu, 24 Sep 2026 16:34:10 +0200 Subject: [PATCH RFC 2/4] sysctl: Apply sysctl context when flag is active Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260924-lklm-sysctl-headerctx-template-v1-2-b25e51c66ba7@kernel.org> References: <20260924-lklm-sysctl-headerctx-template-v1-0-b25e51c66ba7@kernel.org> In-Reply-To: <20260924-lklm-sysctl-headerctx-template-v1-0-b25e51c66ba7@kernel.org> To: Kees Cook Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, =?utf-8?q?Ondrej_Mosn=C3=A1=C4=8Dek?= , Andrew Morton , Ryan Roberts , Serge Hallyn , "Eric W . Biederman" , Alexey Gladkov , Joel Granados X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=2730; i=joel.granados@kernel.org; h=from:subject:message-id; bh=I5CKmhNtTnWeuzjiQtc94qyADu0YXow+af+CzKqUVMc=; b=owJ4nAHtARL+kA0DAAoBupfNUreWQU8ByyZiAGq1NOXd5c0dJfW3SBiNoI1dPmuYeuj9U2c8S tTl/ZYcVMuHiokBswQAAQoAHRYhBK5HCVcl5jElzssnkLqXzVK3lkFPBQJqtTTlAAoJELqXzVK3 lkFPQSwL+gMJstW2nqQmHrOX+SDossmZOHPV5GBDoHYK1RjArd8v/8QuPILsP33zPYyzPAE0gLU n6L5Sf5b8KIdQpthCdlmtai56LrUWNZY5pkyE56qYUYyZ7OHKX7QzKOqcLbsSonPDmJn+sgJKvR pLUAycJiLWnMeogMNJ1flpD9OQ7b4VAWDLM+j8BLI0S/OnKWwnogX4cNr4bG8cdkyLfHlDbMiPV wfcJPKIqG0tIWhFjMg3i/Q7s2Y92OxYodwOAyOCjyxgYnJjV7RTi4GAbxuDfy6AE/tZmXfrGE1c WTONmfzMTKjikZjVK/VgZpA0vW3PwiBc6n8eeShbWVP8rm5q38Pir9wokG0zhCbpu6aqssKu33/ 9GDnNFtcBAi6dtJTCcuqwUn/zpOBzHHEgYJEW0NVQ7aTlq6F5FWSzeNOw92oil1FESLqPQEVeTv 7JpxrD9GwJr9CWUsqg6We2T9vSQFRslJZlsoKlbQ+1YVdgItxDLyE8z4+K5RHjtdGhTh7nZe7C8 Ak= X-Developer-Key: i=joel.granados@kernel.org; a=openpgp; fpr=F1F8E46D30F0F6C4A45FF4465895FAAC338C6E77 X-Endpoint-Received: by B4 Relay for joel.granados@kernel.org/default with auth_id=239 Whenever CTL_TABLE_F_CTX_DATA is set on the entry, overlay the ->data entry contained in inst on the entry to be passed to proc_handlers. No table sets the flags yet, so there is no functional change. Signed-off-by: Joel Granados --- fs/proc/proc_sysctl.c | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index fe32337892f9badc897a29e9176e66790003fb05..1ed9f4e1a17e28c5db1d07356390cbee968cb91f 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -550,12 +550,31 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry, return err; } +/* Returns @entry itself when it is not flagged, else a resolved copy in @buf. */ +static const struct ctl_table *sysctl_apply_ctx(struct ctl_table_header *head, + const struct ctl_table *entry, + struct ctl_table *buf) +{ + ptrdiff_t off; + + if (!(entry->flags & CTL_TABLE_F_CTX_DATA)) + return entry; + + off = (const char *)entry->data - (const char *)head->ctx.tmpl; + + *buf = *entry; + buf->data = (char *)head->ctx.inst + off; + + return buf; +} + static ssize_t proc_sys_call_handler(struct kiocb *iocb, struct iov_iter *iter, int write) { struct inode *inode = file_inode(iocb->ki_filp); struct ctl_table_header *head = grab_header(inode); const struct ctl_table *table = PROC_I(inode)->sysctl_entry; + struct ctl_table ctx_entry; size_t count = iov_iter_count(iter); char *kbuf; ssize_t error; @@ -567,6 +586,8 @@ static ssize_t proc_sys_call_handler(struct kiocb *iocb, struct iov_iter *iter, * At this point we know that the sysctl was not unregistered * and won't be until we finish. */ + table = sysctl_apply_ctx(head, table, &ctx_entry); + error = -EPERM; if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ)) goto out; @@ -797,6 +818,7 @@ static int proc_sys_permission(struct mnt_idmap *idmap, */ struct ctl_table_header *head; const struct ctl_table *table; + struct ctl_table ctx_entry; int error; /* Executable files are not allowed under /proc/sys/ */ @@ -810,8 +832,11 @@ static int proc_sys_permission(struct mnt_idmap *idmap, table = PROC_I(inode)->sysctl_entry; if (!table) /* global root - r-xr-xr-x */ error = mask & MAY_WRITE ? -EACCES : 0; - else /* Use the permissions on the sysctl table entry */ + else { + /* ->permissions may inspect the entry, so resolve it first. */ + table = sysctl_apply_ctx(head, table, &ctx_entry); error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK); + } sysctl_head_finish(head); return error; -- 2.50.1