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From 534fd1f0c84b12ba6080a46e07c57ef913c77cba Mon Sep 17 00:00:00 2001
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From: Radovan Sroka <rsroka@redhat.com>
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Date: Thu, 25 Aug 2022 15:38:01 +0200
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Subject: [PATCH] fapolicyd: Make write() nonblocking
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- switch to read only and non blocking mode for pipe
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- add 1 minute loop to wait for pipe to reappear
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Sometimes during the system update/upgrade fapolicyd
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get restarted e.g. when systemd gets updated.
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That can lead to the situation where fapolicyd pipe
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has been removed and created again.
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In such cases rpm-plugin-fapolicyd gets stuck on
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write() to the pipe which does not exist anymore.
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After switching to non blocking file descriptor
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we can try to reopen the pipe if there is an error
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from write(). Assuming that a new pipe should appear
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when fapolicyd daemon starts again.
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If not then after 1 minute of waiting we expect
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fapolicyd daemon to be not active and we let the
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transaction continue.
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Signed-off-by: Radovan Sroka <rsroka@redhat.com>
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---
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 plugins/fapolicyd.c | 74 +++++++++++++++++++++++++++++++++++++++------
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 1 file changed, 65 insertions(+), 9 deletions(-)
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diff --git a/plugins/fapolicyd.c b/plugins/fapolicyd.c
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index 1ff50c30f..6c6322941 100644
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--- a/plugins/fapolicyd.c
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+++ b/plugins/fapolicyd.c
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@@ -27,7 +27,7 @@ static rpmRC open_fifo(struct fapolicyd_data* state)
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     int fd = -1;
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     struct stat s;
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-    fd = open(state->fifo_path, O_RDWR);
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+    fd = open(state->fifo_path, O_WRONLY|O_NONBLOCK);
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     if (fd == -1) {
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         rpmlog(RPMLOG_DEBUG, "Open: %s -> %s\n", state->fifo_path, strerror(errno));
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         goto bad;
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@@ -55,15 +55,26 @@ static rpmRC open_fifo(struct fapolicyd_data* state)
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     }
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     state->fd = fd;
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+
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     /* considering success */
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     return RPMRC_OK;
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  bad:
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     if (fd >= 0)
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         close(fd);
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+
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+    state->fd = -1;
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     return RPMRC_FAIL;
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 }
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+static void close_fifo(struct fapolicyd_data* state)
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+{
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+    if (state->fd > 0)
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+        (void) close(state->fd);
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+
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+    state->fd = -1;
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+}
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+
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 static rpmRC write_fifo(struct fapolicyd_data* state, const char * str)
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 {
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     ssize_t len = strlen(str);
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@@ -86,6 +97,54 @@ static rpmRC write_fifo(struct fapolicyd_data* state, const char * str)
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     return RPMRC_FAIL;
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 }
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+static void try_to_write_to_fifo(struct fapolicyd_data* state, const char * str)
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+{
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+    int reload = 0;
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+    int printed = 0;
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+
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+    /* 1min/60s */
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+    const int timeout = 60;
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+
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+    /* wait up to X seconds */
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+    for (int i = 0; i < timeout; i++) {
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+
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+        if (reload) {
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+            if (!printed) {
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+                rpmlog(RPMLOG_WARNING, "rpm-plugin-fapolicyd: waiting for the service connection to resume, it can take up to %d seconds\n", timeout);
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+                printed = 1;
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+            }
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+
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+            (void) close_fifo(state);
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+            (void) open_fifo(state);
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+        }
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+
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+        if (state->fd >= 0) {
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+            if (write_fifo(state, str) == RPMRC_OK) {
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+
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+                /* write was successful after few reopens */
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+                if (reload)
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+                    rpmlog(RPMLOG_WARNING, "rpm-plugin-fapolicyd: the service connection has resumed\n");
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+
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+                break;
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+            }
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+        }
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+
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+        /* failed write or reopen */
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+        reload = 1;
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+        sleep(1);
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+
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+        /* the last iteration */
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+        /* consider failure */
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+        if (i == timeout-1) {
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+            rpmlog(RPMLOG_WARNING, "rpm-plugin-fapolicyd: the service connection has not resumed\n");
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+            rpmlog(RPMLOG_WARNING, "rpm-plugin-fapolicyd: continuing without the service\n");
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+        }
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+
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+    }
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+
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+}
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+
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+
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 static rpmRC fapolicyd_init(rpmPlugin plugin, rpmts ts)
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 {
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     if (rpmtsFlags(ts) & (RPMTRANS_FLAG_TEST|RPMTRANS_FLAG_BUILD_PROBS))
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@@ -102,10 +161,7 @@ static rpmRC fapolicyd_init(rpmPlugin plugin, rpmts ts)
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 static void fapolicyd_cleanup(rpmPlugin plugin)
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 {
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-    if (fapolicyd_state.fd > 0)
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-        (void) close(fapolicyd_state.fd);
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-
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-    fapolicyd_state.fd = -1;
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+    (void) close_fifo(&fapolicyd_state);
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 }
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 static rpmRC fapolicyd_tsm_post(rpmPlugin plugin, rpmts ts, int res)
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@@ -116,9 +172,9 @@ static rpmRC fapolicyd_tsm_post(rpmPlugin plugin, rpmts ts, int res)
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     /* we are ready */
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     if (fapolicyd_state.fd > 0) {
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         /* send a signal that transaction is over */
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-        (void) write_fifo(&fapolicyd_state, "1\n");
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+        (void) try_to_write_to_fifo(&fapolicyd_state, "1\n");
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         /* flush cache */
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-        (void) write_fifo(&fapolicyd_state, "2\n");
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+        (void) try_to_write_to_fifo(&fapolicyd_state, "2\n");
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     }
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  end:
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@@ -133,7 +189,7 @@ static rpmRC fapolicyd_scriptlet_pre(rpmPlugin plugin, const char *s_name,
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     if (fapolicyd_state.changed_files > 0) {
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         /* send signal to flush cache */
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-        (void) write_fifo(&fapolicyd_state, "2\n");
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+        (void) try_to_write_to_fifo(&fapolicyd_state, "2\n");
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         /* optimize flushing */
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         /* flush only when there was an actual change */
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@@ -176,7 +232,7 @@ static rpmRC fapolicyd_fsm_file_prepare(rpmPlugin plugin, rpmfi fi,
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     char * sha = rpmfiFDigestHex(fi, NULL);
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     snprintf(buffer, 4096, "%s %lu %64s\n", dest, size, sha);
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-    (void) write_fifo(&fapolicyd_state, buffer);
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+    (void) try_to_write_to_fifo(&fapolicyd_state, buffer);
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     free(sha);
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-- 
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2.37.3
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