From 1faf3a963c5ba9ab57f0683e9ceaf5ebf60c566d Mon Sep 17 00:00:00 2001
From: Thomas Blume <Thomas.Blume@suse.com>
Date: Mon, 17 Apr 2023 15:41:07 +0200
Subject: [PATCH] feat(livenet): add memory size check depending on live image
 size

For writeable live images, the memory must hold the complete image.
That means it must be at least the size of the image plus some RAM
necessary to run processes.
With too small RAM, the OOM Killer steps in and makes the boot hang.
This patch lets the system go into the emergency shell instead.

The default minimum RAM after subtracting the live image size is set to 1G.
The parameter rd.minmem is added to modify this.
---
 man/dracut.cmdline.7.asc                      |  7 ++++++
 .../90dmsquash-live/dmsquash-live-root.sh     |  2 ++
 modules.d/90livenet/livenetroot.sh            |  7 ++++++
 modules.d/99base/dracut-lib.sh                | 25 +++++++++++++++++++
 4 files changed, 41 insertions(+)

diff --git a/man/dracut.cmdline.7.asc b/man/dracut.cmdline.7.asc
index e8610399d5..95cfc2cb9a 100644
--- a/man/dracut.cmdline.7.asc
+++ b/man/dracut.cmdline.7.asc
@@ -1117,6 +1117,13 @@ NOTE: There must be enough free RAM available to hold the complete image.
 +
 This method is very suitable for diskless boots.
 
+**rd.minmem=**__<megabyte>__::
+Specify minimum free RAM in MB after copying a live disk image into memory.
+The default is 1024.
++
+This parameter only applies together with the parameters rd.writable.fsimg
+or rd.live.ram.
+
 **root=**live:__<url>__::
 Boots a live image retrieved from __<url>__.  Requires the dracut 'livenet'
 module.  Valid handlers: __http, https, ftp, torrent, tftp__.
diff --git a/modules.d/90dmsquash-live/dmsquash-live-root.sh b/modules.d/90dmsquash-live/dmsquash-live-root.sh
index a98e258c26..705f1267f0 100755
--- a/modules.d/90dmsquash-live/dmsquash-live-root.sh
+++ b/modules.d/90dmsquash-live/dmsquash-live-root.sh
@@ -314,6 +314,8 @@ if [ -e /run/initramfs/live/${live_dir}/${squash_image} ]; then
 fi
 if [ -e "$SQUASHED" ]; then
     if [ -n "$live_ram" ]; then
+        imgsize=$(($(stat -c %s -- $SQUASHED) / (1024 * 1024)))
+        check_live_ram $imgsize
         echo 'Copying live image to RAM...' > /dev/kmsg
         echo ' (this may take a minute)' > /dev/kmsg
         dd if=$SQUASHED of=/run/initramfs/squashed.img bs=512 2> /dev/null
diff --git a/modules.d/90livenet/livenetroot.sh b/modules.d/90livenet/livenetroot.sh
index 92ad805bed..66dd41b39a 100755
--- a/modules.d/90livenet/livenetroot.sh
+++ b/modules.d/90livenet/livenetroot.sh
@@ -16,6 +16,13 @@ netroot="$2"
 liveurl="${netroot#livenet:}"
 info "fetching $liveurl"
 
+if getargbool 0 'rd.writable.fsimg'; then
+
+    imgsize=$(($(curl -sIL "$liveurl" | sed -n 's/Content-Length: *\([[:digit:]]*\).*/\1/p') / (1024 * 1024)))
+
+    check_live_ram $imgsize
+fi
+
 imgfile=
 #retry until the imgfile is populated with data or the max retries
 i=1
diff --git a/modules.d/99base/dracut-lib.sh b/modules.d/99base/dracut-lib.sh
index 6eaa0fe149..a8ca2c96eb 100755
--- a/modules.d/99base/dracut-lib.sh
+++ b/modules.d/99base/dracut-lib.sh
@@ -1151,3 +1151,28 @@ load_fstype() {
     done < /proc/filesystems
     modprobe "$1"
 }
+
+# parameter: size of live image
+# calls emergency shell if ram size is too small for the image
+check_live_ram() {
+    minmem=$(getarg rd.minmem)
+    minmem=${minmem:-1024}
+    imgsize=$1
+    memsize=$(($(sed -n 's/MemTotal: *\([[:digit:]]*\).*/\1/p' /proc/meminfo) / 1024))
+
+    if [ -z "$imgsize" ]; then
+        warn "Image size could not be determined"
+        return 0
+    fi
+
+    if [ $((memsize - imgsize)) -lt "$minmem" ]; then
+        sed -i "N;/and attach it to a bug report./s/echo$/echo\n\
+         echo \n\
+         echo 'Warning!!!'\n\
+         echo 'The memory size of your system is too small for this live image.'\n\
+         echo 'Expect killed processes due to out of memory conditions.'\n\
+         echo \n/" /usr/bin/dracut-emergency
+
+        emergency_shell
+    fi
+}