Merge upstream branch 'main'

.github/workflows/builds.yml

@@ -36,7 +36,8 @@ jobs:
               libdbus-1-dev \
               libpam0g-dev \
               libseccomp-dev \
-              libselinux1-dev
+              libselinux1-dev \
+              liburing-dev
 
       - name: Checkout the packaging branch
         run: |

.github/workflows/tests.yml

@@ -44,6 +44,9 @@ jobs:
           - ubuntu-24.04
           - ubuntu-22.04-arm
           - ubuntu-24.04-arm
+        async-api:
+          - epoll
+          - io_uring
         variant:
           - default
           - sanitizer
@@ -54,6 +57,10 @@ jobs:
             os: ubuntu-22.04-arm
           - variant: sanitizer
             os: ubuntu-24.04-arm
+          - async-api: io_uring
+            os: ubuntu-22.04-arm
+          - async-api: io_uring
+            os: ubuntu-22.04
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout code
@@ -75,7 +82,8 @@ jobs:
               libdbus-1-dev \
               libpam0g-dev \
               libseccomp-dev \
-              libselinux1-dev
+              libselinux1-dev \
+              liburing-dev
 
       - name: Compiler version
         env:
@@ -97,6 +105,7 @@ jobs:
           if [ "${{ matrix.variant }}" = "default" ]; then
               meson setup build \
                   -Dprefix=/usr \
+                  -Dio-uring-event-loop=${{ matrix.async-api == 'io_uring' }} \
                   -Dtests=true \
                   -Dpam-cgroup=true \
                   -Dtools-multicall=true \
@@ -106,12 +115,12 @@ jobs:
           elif [ "${{ matrix.variant }}" = "sanitizer" ]; then
               meson setup build \
                   -Dprefix=/usr \
+                  -Dio-uring-event-loop=${{ matrix.async-api == 'io_uring' }} \
                   -Dtests=true \
                   -Dpam-cgroup=true \
                   -Dtools-multicall=true \
                   -Dwerror=true \
                   -Db_lto_mode=default \
-                  -Dio-uring-event-loop=false \
                   -Db_lundef=false \
                   -Db_sanitize=address,undefined
           fi

src/lxc/file_utils.c

@@ -11,6 +11,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <time.h>
+#include <poll.h>
 
 #include "file_utils.h"
 #include "macro.h"
@@ -147,6 +148,91 @@ ssize_t lxc_read_try_buf_at(int dfd, const char *path, void *buf, size_t count)
 	return ret;
 }
 
+static int __lxc_wait_for_io_ready(int fd, int event, int timeout_ms)
+{
+	int ret;
+	struct pollfd pfd = {
+		.fd = fd,
+		.events = event,
+		.revents = 0
+	};
+
+	do {
+		ret = poll(&pfd, 1, timeout_ms);
+	} while (ret < 0 && errno == EINTR);
+
+	if (ret < 0)
+		return -errno;
+
+	if (ret == 0)
+		return -ETIMEDOUT;
+
+	if (pfd.revents & (POLLERR | POLLHUP | POLLNVAL)) {
+		if (pfd.revents & POLLERR)
+			return -EPIPE;
+		if (pfd.revents & POLLHUP)
+			return -EPIPE;
+		if (pfd.revents & POLLNVAL)
+			return -EBADF;
+	}
+
+	if (!(pfd.revents & event))
+		return -EAGAIN;
+
+	return ret;
+}
+
+ssize_t lxc_write_all(int fd, const void *buf, size_t count)
+{
+	ssize_t left_to_write = count;
+	const char *ptr = buf;
+	int flags;
+
+	flags = fcntl(fd, F_GETFL);
+	if (flags < 0)
+		return ret_set_errno(-1, errno);
+
+	/* only non-blocking fds are allowed */
+	if (!(flags & O_NONBLOCK))
+		return ret_set_errno(-1, EINVAL);
+
+	while (left_to_write > 0) {
+		int ret = write(fd, ptr, left_to_write);
+
+		if (ret > 0) {
+			left_to_write -= ret;
+			ptr += ret;
+			continue;
+		}
+
+		if (ret == 0)
+			break;
+
+		/* ret < 0 */
+		if (errno == EINTR)
+			continue;
+
+		if (errno == EAGAIN) {
+			int pret = __lxc_wait_for_io_ready(fd, POLLOUT, 5000);
+
+			/* we've got an event on fd */
+			if (pret > 0)
+				continue;
+
+			if (pret == -ETIMEDOUT)
+				break;
+
+			if (pret < 0)
+				return ret_set_errno(-1, -pret);
+		}
+
+		/* some other error */
+		return ret_set_errno(-1, errno);
+	}
+
+	return count - left_to_write;
+}
+
 ssize_t lxc_write_nointr(int fd, const void *buf, size_t count)
 {
 	ssize_t ret;

src/lxc/file_utils.h

@@ -35,6 +35,8 @@ __hidden extern int lxc_read_from_file(const char *filename, void *buf, size_t c
     __access_w(2, 3);
 
 /* send and receive buffers completely */
+__hidden extern ssize_t lxc_write_all(int fd, const void *buf, size_t count) __access_r(2, 3);
+
 __hidden extern ssize_t lxc_write_nointr(int fd, const void *buf, size_t count) __access_r(2, 3);
 
 __hidden extern ssize_t lxc_pwrite_nointr(int fd, const void *buf, size_t count, off_t offset)

src/lxc/terminal.c

@@ -338,7 +338,7 @@ static int lxc_terminal_ptx_io(struct lxc_terminal *terminal)
 	w_rbuf = w_log = 0;
 	/* write to peer first */
 	if (terminal->peer >= 0)
-		w = lxc_write_nointr(terminal->peer, buf, r);
+		w = lxc_write_all(terminal->peer, buf, r);
 
 	/* write to terminal ringbuffer */
 	if (terminal->buffer_size > 0)
@@ -375,7 +375,7 @@ static int lxc_terminal_peer_io(struct lxc_terminal *terminal)
 		return -1;
 	}
 
-	w = lxc_write_nointr(terminal->ptx, buf, r);
+	w = lxc_write_all(terminal->ptx, buf, r);
 	if (w != r)
 		WARN("Short write on terminal r:%d != w:%d", r, w);
 

src/tests/lxc-test-lxc-attach

@@ -58,6 +58,7 @@ for i in $(seq 1 100); do
 	if [ "$attach" != "busy" ]; then
 		FAIL "lxc-attach -n busy -- hostname"
 	fi
+	rm -f "${ATTACH_LOG}"
 done
 
 # stdin  --> /dev/null
@@ -67,6 +68,7 @@ attach=$(lxc-attach -n busy -l trace -o "${ATTACH_LOG}" -- hostname < /dev/null
 if [ "$attach" != "busy" ]; then
         FAIL "lxc-attach -n busy -- hostname < /dev/null"
 fi
+rm -f "${ATTACH_LOG}"
 
 # stdin  --> attached to pty
 # stdout --> /dev/null
@@ -75,6 +77,7 @@ attach=$(lxc-attach -n busy -l trace -o "${ATTACH_LOG}" -- hostname > /dev/null
 if [ -n "$attach" ]; then
         FAIL "lxc-attach -n busy -- hostname > /dev/null"
 fi
+rm -f "${ATTACH_LOG}"
 
 # stdin  --> attached to pty
 # stdout --> attached to pty
@@ -83,6 +86,7 @@ attach=$(lxc-attach -n busy -l trace -o "${ATTACH_LOG}" -- hostname 2> /dev/null
 if [ "$attach" != "busy" ]; then
         FAIL "lxc-attach -n busy -- hostname 2> /dev/null < /dev/null"
 fi
+rm -f "${ATTACH_LOG}"
 
 # stdin  --> /dev/null
 # stdout --> attached to pty
@@ -91,6 +95,7 @@ attach=$(lxc-attach -n busy -l trace -o "${ATTACH_LOG}" -- hostname 2> /dev/null
 if [ "$attach" != "busy" ]; then
         FAIL "lxc-attach -n busy -- hostname 2> /dev/null < /dev/null"
 fi
+rm -f "${ATTACH_LOG}"
 
 # Use a synthetic reproducer in container to produce output on stderr. stdout on
 # the host gets redirect to /dev/null. We should still be able to receive
@@ -104,6 +109,7 @@ attach=$( ( lxc-attach -n busy -l trace -o "${ATTACH_LOG}" -- sh -c 'hostname >&
 if [ "$attach" != "busy" ]; then
         FAIL "lxc-attach -n busy -- sh -c 'hostname >&2' > /dev/null"
 fi
+rm -f "${ATTACH_LOG}"
 
 # Use a synthetic reproducer in container to produce output on stderr. stderr on
 # the host gets redirect to /dev/null. We should not receive output on stderr on
@@ -116,7 +122,7 @@ attach=$( ( lxc-attach -n busy -l trace -o "${ATTACH_LOG}" -- sh -c 'hostname >&
 if [ -n "$attach" ]; then
         FAIL "lxc-attach -n busy -- sh -c 'hostname >&2' 2> /dev/null"
 fi
-
+rm -f "${ATTACH_LOG}"
 
 # stdin  --> attached to pty
 # stdout --> /dev/null
@@ -126,7 +132,7 @@ attach=$(lxc-attach -n busy -l trace -o "${ATTACH_LOG}" -- sh -c 'rm 2>&1' > /de
 if [ -n "$attach" ]; then
         FAIL "lxc-attach -n busy -- sh -c 'rm 2>&1' > /dev/null"
 fi
-
+rm -f "${ATTACH_LOG}"
 
 # - stdin  --> attached to pty
 # - stdout --> attached to pty
@@ -136,6 +142,7 @@ attach=$(lxc-attach -n busy -l trace -o "${ATTACH_LOG}" -- sh -c 'rm 2>&1' 2> /d
 if [ -z "$attach" ]; then
         FAIL "lxc-attach -n busy -- sh -c 'rm 2>&1' 2> /dev/null"
 fi
+rm -f "${ATTACH_LOG}"
 
 # stdin  --> $in
 # stdout --> attached to pty
@@ -144,6 +151,7 @@ attach=$(echo hostname | lxc-attach -n busy -l trace -o "${ATTACH_LOG}" -- || FA
 if [ "$attach" != "busy" ]; then
         FAIL "echo hostname | lxc-attach -n busy --"
 fi
+rm -f "${ATTACH_LOG}"
 
 # stdin  --> attached to pty
 # stdout --> $out
@@ -158,7 +166,7 @@ if [ "$outcontent" != "OUT" ] || [ "$errcontent" != "ERR" ]; then
         FAIL "lxc-attach -n busy -- sh -c 'echo OUT; echo ERR >&2' > $out 2> $err"
 fi
 
-rm -f $out $err
+rm -f $out $err "${ATTACH_LOG}"
 
 # stdin  --> $in
 # stdout --> $out
@@ -174,8 +182,57 @@ if [ "$outcontent" != "busy" ] || [ -z "$errcontent" ]; then
         FAIL "echo 'hostname; rm' | lxc-attach -n busy > $out 2> $err"
 fi
 
-rm -f $out $err
+rm -f $out $err "${ATTACH_LOG}"
+
+#
+# This testcase covers cases like:
+# https://github.com/lxc/lxc/issues/4546
+# https://discuss.linuxcontainers.org/t/lxc-attach-long-output-stops-suddenly-possible-bug/22031
+# https://discuss.linuxcontainers.org/t/fixing-forgejo-runners-lxc-logging/25918
+#
+# Idea is simple, we simulate a heavy IO and write relatively large amount of data to overfill
+# pts device buffers, then ensure data integrity.
+#
+# We need to use "script" tool to allocate TTYs properly, otherwise we don't go into a
+# problematic LXC code-path we want to cover.
+#
+# Also, I had to introduce two synthetic sleeps: one before issuing commands to busybox shell inside
+# a container and another one after.
+#
+# First one is needed, because LXC looses some pieces of terminal device input during
+# lxc-attach command initialization because of tcsetattr(fd, TCSAFLUSH, &newtios) call
+# (see https://github.com/lxc/lxc/blob/5d9839bc1316fa185d8c29b90982684b32e3dfa7/src/lxc/terminal.c#L523)
+# I would replace TCSAFLUSH with TCSANOW to avoid TTY buffer flush (and I tested that it helps),
+# but taking into account that this code is here since 2010
+# (see https://github.com/lxc/lxc/commit/e0dc0de76ed1ad9e284a37bd01268227d4eae8c9)
+# I decided to keep it like it is for now (FIXME?).
+#
+# Second sleep is needed because of a bug in busybox, unfortunately, without this sleep,
+# busybox fails to react on the host pipe write-end closure (after full command submission)
+# and continues to poll infinitely. This sleep makes pipe closure even to be separated from
+# a heavy IO and avoids this bug.
+#
+
+# Check test dependencies
+command -v script >/dev/null 2>&1 || { echo "'script' command is missing" >&2; exit 1; }
+busybox dd --help >/dev/null 2>&1 || FAIL "missing busybox's dd applet"
+busybox hexdump --help >/dev/null 2>&1 || FAIL "missing busybox's hexdump applet"
+busybox tee --help >/dev/null 2>&1 || FAIL "missing busybox's tee applet"
+
+out=$(mktemp /tmp/out_XXXX)
+BS=1000000
+( sleep 3; echo "echo DATASTART ; dd if=/dev/urandom bs=$BS count=1 status=none | hexdump | tee /root/large-data.txt ; echo DATAEND" ; sleep 1 ) | \
+	script -q -e -c "lxc-attach -n busy -l trace -o \"${ATTACH_LOG}\"" | \
+	sed -n '/DATASTART/,/DATAEND/{/DATASTART/d;/DATAEND/d;s/[\r\n]*$//;p}' > $out
+
+[ $(stat -c%s $out) -gt $BS ] || FAIL "generated file size is too small"
+cmp -s /var/lib/lxc/busy/rootfs/root/large-data.txt $out || FAIL "data corruption detected"
+
+md5sum /var/lib/lxc/busy/rootfs/root/large-data.txt $out
+ls -lah /var/lib/lxc/busy/rootfs/root/large-data.txt
+rm -f /var/lib/lxc/busy/rootfs/root/large-data.txt $out "${ATTACH_LOG}"
 
+# Cleanup stage
 lxc-destroy -n busy -f
 rm -f "${ATTACH_LOG}" || true