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From: Rodrigo Campos <rodrigo@sdfg.com.ar>
To: fstests@vger.kernel.org
Cc: Christian Brauner <brauner@kernel.org>,
	Giuseppe Scrivano <gscrivan@redhat.com>,
	Rodrigo Campos <rodrigo@sdfg.com.ar>
Subject: [PATCH 04/11] vfs: Make switch_userns set PR_SET_DUMPABLE
Date: Tue,  7 Mar 2023 12:45:00 +0100	[thread overview]
Message-ID: <20230307114507.332309-5-rodrigo@sdfg.com.ar> (raw)
In-Reply-To: <20230307114507.332309-1-rodrigo@sdfg.com.ar>

We need PR_SET_DUMPABLE in order to write the mapping files when
creating a userns. From prctl(2) PR_SET_DUMPABLE is reset when the
process's effective user or group ID is changed.

As we are changing the EUID here, we also reset it to allow creating
nested userns with subsequent switch_users() calls.

This was not causing any issues because we weren't using switch_users()
to create nested userns. Nested userns were created with
userns_fd_cb()/create_userns_hierarchy() that set PR_SET_DUMPABLE.

Future patches will rely on switch_users() to create nested userns. So
this patch fixes that.

Signed-off-by: Rodrigo Campos <rodrigo@sdfg.com.ar>
---
 src/vfs/utils.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git src/vfs/utils.c src/vfs/utils.c
index 67779e83..ab92c743 100644
--- src/vfs/utils.c
+++ src/vfs/utils.c
@@ -285,6 +285,10 @@ bool switch_ids(uid_t uid, gid_t gid)
 	if (setresuid(uid, uid, uid))
 		return syserror("failure: setresuid");
 
+	/* Ensure we can access proc files from processes we can ptrace. */
+	if (prctl(PR_SET_DUMPABLE, 1, 0, 0, 0))
+		return syserror("failure: make dumpable");
+
 	return true;
 }
 
@@ -302,11 +306,6 @@ static int userns_fd_cb(void *data)
 	if (c == '1') {
 		if (!switch_ids(0, 0))
 			return syserror("failure: switch ids to 0");
-
-		/* Ensure we can access proc files from processes we can ptrace. */
-		ret = prctl(PR_SET_DUMPABLE, 1, 0, 0, 0);
-		if (ret < 0)
-			return syserror("failure: make dumpable");
 	}
 
 	ret = write_nointr(h->fd_event, "1", 1);
-- 
2.39.2


  parent reply	other threads:[~2023-03-07 12:05 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-07 11:44 [PATCH 00/11] Tests for idmapped tmpfs Rodrigo Campos
2023-03-07 11:44 ` [PATCH 01/11] vfs: Don't open-code safe_close() Rodrigo Campos
2023-03-07 16:42   ` Christian Brauner
2023-03-07 11:44 ` [PATCH 02/11] vfs: Fix documentation typo Rodrigo Campos
2023-03-07 16:43   ` Christian Brauner
2023-03-07 11:44 ` [PATCH 03/11] vfs: Fix race condition on get_userns_fd() Rodrigo Campos
2023-03-07 16:46   ` Christian Brauner
2023-03-07 17:32     ` Rodrigo Campos
2023-03-07 11:45 ` Rodrigo Campos [this message]
2023-03-07 16:47   ` [PATCH 04/11] vfs: Make switch_userns set PR_SET_DUMPABLE Christian Brauner
2023-03-07 11:45 ` [PATCH 05/11] vfs: Specify wether a test is run inside a userns or not Rodrigo Campos
2023-03-07 11:45 ` [PATCH 06/11] vfs: Prepare tests in &s_idmapped_mounts to be reused inside a userns Rodrigo Campos
2023-03-07 16:50   ` Christian Brauner
2023-03-07 23:34     ` Rodrigo Campos
2023-03-13 10:37       ` Christian Brauner
2023-03-07 11:45 ` [PATCH 07/11] vfs: Make idmapped core tests public Rodrigo Campos
2023-03-07 16:51   ` Christian Brauner
2023-03-07 11:45 ` [PATCH 08/11] vfs: Export test_setup() and test_cleanup() Rodrigo Campos
2023-03-07 16:51   ` Christian Brauner
2023-03-07 17:11     ` Rodrigo Campos
2023-03-07 11:45 ` [PATCH 09/11] vfs: Add DIR0 constant Rodrigo Campos
2023-03-07 16:53   ` Christian Brauner
2023-03-07 17:33     ` Rodrigo Campos
2023-03-07 11:45 ` [PATCH 10/11] vfs: Add tmpfs tests for idmap mounts Rodrigo Campos
2023-03-07 11:45 ` [PATCH 11/11] vfs: Use tabs to indent, not spaces Rodrigo Campos
2023-03-07 16:55   ` Christian Brauner
2023-03-07 17:10     ` Rodrigo Campos
2023-03-08 17:27     ` Zorro Lang

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