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Merge pull request #1147 from joe-lawrence/unload-retry-module-refcnt

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kpatch: wait for module ref counts on unload
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Joe Lawrence 2020-11-19 11:47:48 -05:00 committed by GitHub
commit 158efe3191
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1 changed files with 38 additions and 2 deletions
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@ -28,6 +28,7 @@ SCRIPTDIR="$(readlink -f "$(dirname "$(type -p "$0")")")"
VERSION="0.9.2"
POST_ENABLE_WAIT=15 # seconds
POST_SIGNAL_WAIT=60 # seconds
MODULE_REF_WAIT=15 # seconds
# How many times to try loading the patch if activeness safety check fails.
MAX_LOAD_ATTEMPTS=5
@ -125,6 +126,10 @@ find_core_module() {
return 1
}
kpatch_core_loaded() {
grep -q -e "T kpatch_register" /proc/kallsyms
}
core_loaded () {
grep -q -e "T klp_enable_patch" -e "T kpatch_register" /proc/kallsyms
}
@ -265,6 +270,31 @@ wait_for_patch_transition() {
return 1
}
module_ref_count() {
local modname="$1"
[[ $(cat "/sys/module/$modname/refcnt" 2>/dev/null) != "0" ]]
}
wait_for_zero_module_ref_count() {
local modname="$1"
local i=0
# We can't rely on a zero refcount with kpatch.ko as it
# implements KPATCH_FORCE_UNSAFE with an additional reference on
# kpatch-patch modules to avoid potential crashes.
kpatch_core_loaded && return 0
module_ref_count "$modname" || return 0
echo "waiting (up to $MODULE_REF_WAIT seconds) for module refcount..."
for (( i=0; i<MODULE_REF_WAIT; i++ )); do
module_ref_count "$modname" || return 0
sleep 1s
done
return 1
}
load_module () {
local module="$1"
@ -381,10 +411,16 @@ disable_patch_strict () {
}
remove_module () {
echo "unloading patch module: $1"
local modname="$1"
if ! wait_for_zero_module_ref_count "$modname"; then
die "failed to unload module $modname (refcnt)"
fi
echo "unloading patch module: $modname"
# ignore any error here because rmmod can fail if the module used
# KPATCH_FORCE_UNSAFE.
rmmod "$1" 2> /dev/null || return 0
rmmod "$modname" 2> /dev/null || return 0
}
unload_module () {