From: David Gibson <david@gibson.dropbear.id.au>
To: passt-dev@passt.top
Subject: [PATCH v2 15/32] Safer handling if we can't open /proc/self/uid_map
Date: Thu, 08 Sep 2022 16:16:04 +1000 [thread overview]
Message-ID: <20220908061621.2430844-16-david@gibson.dropbear.id.au> (raw)
In-Reply-To: <20220908061621.2430844-1-david@gibson.dropbear.id.au>
[-- Attachment #1: Type: text/plain, Size: 1524 bytes --]
passt is allowed to run as "root" (UID 0) in a user namespace, but notas
real root in the init namespace. We read /proc/self/uid_map to determine
if we're in the init namespace or not.
If we're unable to open /proc/self/uid_map we assume we're ok and continue
running as UID 0. This seems unwise: AFAIK the only instance in which
uid_map won't be available is if we're running on a kernel which doesn't
support user namespaces, in which case we won't be able to sandbox
ourselves as we want and fail anyway. If there are other circumstances
where it can't be opened it seems marginally more likely that we *are*
in the init namespace.
Therefore, fail with an error in this case, instead of carrying on.
Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
conf.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/conf.c b/conf.c
index 5c293b5..f1aaa8a 100644
--- a/conf.c
+++ b/conf.c
@@ -1054,8 +1054,12 @@ static int conf_ugid(const char *runas, uid_t *uid, gid_t *gid)
return 0;
/* ..or at least not root in the init namespace.. */
- if ((fd = open("/proc/self/uid_map", O_RDONLY | O_CLOEXEC)) < 0)
- return 0;
+ if ((fd = open("/proc/self/uid_map", O_RDONLY | O_CLOEXEC)) < 0) {
+ ret = -errno;
+ err("Can't determine if we're in init namespace: %s",
+ strerror(-ret));
+ return ret;
+ }
if (read(fd, buf, BUFSIZ) != sizeof(root_uid_map) ||
strncmp(buf, root_uid_map, sizeof(root_uid_map) - 1)) {
--
@@ -1054,8 +1054,12 @@ static int conf_ugid(const char *runas, uid_t *uid, gid_t *gid)
return 0;
/* ..or at least not root in the init namespace.. */
- if ((fd = open("/proc/self/uid_map", O_RDONLY | O_CLOEXEC)) < 0)
- return 0;
+ if ((fd = open("/proc/self/uid_map", O_RDONLY | O_CLOEXEC)) < 0) {
+ ret = -errno;
+ err("Can't determine if we're in init namespace: %s",
+ strerror(-ret));
+ return ret;
+ }
if (read(fd, buf, BUFSIZ) != sizeof(root_uid_map) ||
strncmp(buf, root_uid_map, sizeof(root_uid_map) - 1)) {
--
2.37.3
next prev parent reply other threads:[~2022-09-08 6:16 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-08 6:15 [PATCH v2 00/32] Improve handling of test temporary files David Gibson
2022-09-08 6:15 ` [PATCH v2 01/32] test: Correctly match "background" with "wait" commands David Gibson
2022-09-08 6:15 ` [PATCH v2 02/32] test: Context execution helpers David Gibson
2022-09-08 6:15 ` [PATCH v2 03/32] test: Allow a tmux pane to watch commands executed in contexts David Gibson
2022-09-08 6:15 ` [PATCH v2 04/32] test: Integration of old-style pane execution and new context execution David Gibson
2022-09-08 6:15 ` [PATCH v2 05/32] test: Issue host commands via context for most tests David Gibson
2022-09-08 6:15 ` [PATCH v2 06/32] test: Use new-style contexts for passt pane in the pasta and passt tests David Gibson
2022-09-08 6:15 ` [PATCH v2 07/32] test: Add nsholder utility David Gibson
2022-09-08 6:15 ` [PATCH v2 08/32] test: Extend context system to run commands in namespace for pasta tests David Gibson
2022-09-08 6:15 ` [PATCH v2 09/32] test: Use context system for guest commands David Gibson
2022-09-08 6:15 ` [PATCH v2 10/32] test: Use context system for two_guests tests David Gibson
2022-09-08 6:16 ` [PATCH v2 11/32] test: Use new-style command issue for passt_in_ns tests David Gibson
2022-09-08 6:16 ` [PATCH v2 12/32] Don't store UID & GID persistently in the context structure David Gibson
2022-09-08 6:16 ` [PATCH v2 13/32] Split checking for root from dropping root privilege David Gibson
2022-09-08 6:16 ` [PATCH v2 14/32] Consolidate determination of UID/GID to run as David Gibson
2022-09-08 6:16 ` David Gibson [this message]
2022-09-08 6:16 ` [PATCH v2 16/32] Move self-isolation code into a separate file David Gibson
2022-09-08 6:16 ` [PATCH v2 17/32] Consolidate validation of pasta namespace options David Gibson
2022-09-08 6:16 ` [PATCH v2 18/32] Clean up and rename conf_ns_open() David Gibson
2022-09-08 6:16 ` [PATCH v2 19/32] Correctly handle --netns-only in pasta_start_ns() David Gibson
2022-09-08 6:16 ` [PATCH v2 20/32] Handle userns isolation and dropping root at the same time David Gibson
2022-09-08 6:16 ` [PATCH v2 21/32] Allow --userns when pasta spawns a command David Gibson
2022-09-08 6:16 ` [PATCH v2 22/32] test: Group tests by context then protocol, rather than the reverse David Gibson
2022-09-08 6:16 ` [PATCH v2 23/32] test: Remove unused variable FFMPEG_PID_FILE David Gibson
2022-09-08 6:16 ` [PATCH v2 24/32] test: Actually run cleanup function David Gibson
2022-09-08 6:16 ` [PATCH v2 25/32] test: Create common state directories for temporary files David Gibson
2022-09-08 6:16 ` [PATCH v2 26/32] test: Move context temporary files to state dir David Gibson
2022-09-08 6:16 ` [PATCH v2 27/32] test: Dont regnerate small test file in pasta/tcp David Gibson
2022-09-08 6:16 ` [PATCH v2 28/32] test: Use paths in __STATEDIR__ instead of 'temp' and 'tempdir' directives David Gibson
2022-09-08 6:16 ` [PATCH v2 29/32] test: Move pause temporary file to state directory David Gibson
2022-09-08 6:16 ` [PATCH v2 30/32] test: Store pcap files in $LOGDIR instead of /tmp David Gibson
2022-09-08 6:16 ` [PATCH v2 31/32] test: Move pidfiles and nsholder sockets into state directory David Gibson
2022-09-08 6:16 ` [PATCH v2 32/32] test: Move video processing files to $STATEBASE David Gibson
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