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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 17/17] watch_queue: sample: Display superblock notifications [ver #5] From: David Howells To: torvalds@linux-foundation.org, viro@zeniv.linux.org.uk Cc: dhowells@redhat.com, casey@schaufler-ca.com, sds@tycho.nsa.gov, nicolas.dichtel@6wind.com, raven@themaw.net, christian@brauner.io, andres@anarazel.de, jlayton@redhat.com, dray@redhat.com, kzak@redhat.com, keyrings@vger.kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 18 Mar 2020 15:05:49 +0000 Message-ID: <158454394905.2863966.8800154491320171728.stgit@warthog.procyon.org.uk> In-Reply-To: <158454378820.2863966.10496767254293183123.stgit@warthog.procyon.org.uk> References: <158454378820.2863966.10496767254293183123.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.21 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: The notification is run as: ./watch_test and it then watches "/mnt" for superblock notifications: # mount -t tmpfs none /mnt # ./watch_test & # mount -o remount,ro /mnt # mount -o remount,rw /mnt producing: # ./watch_test NOTIFY[000]: ty=000003 sy=00 i=03010010 SUPER 157eb57ca7 change=0[readonly] read() = 16 NOTIFY[000]: ty=000002 sy=04 i=02010010 MOUNT 000001a0 change=4[setattr] aux=0 read() = 16 NOTIFY[000]: ty=000002 sy=04 i=02010010 MOUNT 000001a0 change=4[setattr] aux=0 Signed-off-by: David Howells --- samples/watch_queue/watch_test.c | 39 +++++++++++++++++++++++++++++++++++++- 1 file changed, 38 insertions(+), 1 deletion(-) diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c index 36caaea5261f..734786bd9764 100644 --- a/samples/watch_queue/watch_test.c +++ b/samples/watch_queue/watch_test.c @@ -29,6 +29,9 @@ #ifndef __NR_watch_mount #define __NR_watch_mount -1 #endif +#ifndef __NR_watch_sb +#define __NR_watch_sb -1 +#endif #define BUF_SIZE 256 @@ -87,6 +90,24 @@ static void saw_mount_change(struct watch_notification *n, size_t len) } +static const char *super_subtypes[256] = { + [NOTIFY_SUPERBLOCK_READONLY] = "readonly", + [NOTIFY_SUPERBLOCK_ERROR] = "error", + [NOTIFY_SUPERBLOCK_EDQUOT] = "edquot", + [NOTIFY_SUPERBLOCK_NETWORK] = "network", +}; + +static void saw_super_change(struct watch_notification *n, size_t len) +{ + struct superblock_notification *s = (struct superblock_notification *)n; + + if (len < sizeof(struct superblock_notification)) + return; + + printf("SUPER %08llx change=%u[%s]\n", + s->sb_id, n->subtype, super_subtypes[n->subtype]); +} + /* * Consume and display events. */ @@ -166,6 +187,9 @@ static void consumer(int fd) case WATCH_TYPE_MOUNT_NOTIFY: saw_mount_change(&n.n, len); break; + case WATCH_TYPE_SB_NOTIFY: + saw_super_change(&n.n, len); + break; } p += len; @@ -174,7 +198,7 @@ static void consumer(int fd) } static struct watch_notification_filter filter = { - .nr_filters = 2, + .nr_filters = 3, .filters = { [0] = { .type = WATCH_TYPE_KEY_NOTIFY, @@ -185,6 +209,14 @@ static struct watch_notification_filter filter = { // Reject move-from notifications .subtype_filter[0] = UINT_MAX & ~(1 << NOTIFY_MOUNT_MOVE_FROM), }, + [2] = { + .type = WATCH_TYPE_SB_NOTIFY, + // Only accept notification of changes to R/O state + .subtype_filter[0] = (1 << NOTIFY_SUPERBLOCK_READONLY), + // Only accept notifications of change-to-R/O + .info_mask = WATCH_INFO_FLAG_0, + .info_filter = WATCH_INFO_FLAG_0, + }, }, }; @@ -223,6 +255,11 @@ int main(int argc, char **argv) exit(1); } + if (syscall(__NR_watch_sb, AT_FDCWD, "/mnt", 0, fd, 0x03) == -1) { + perror("watch_sb"); + exit(1); + } + consumer(fd); exit(0); }