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topjohnwu 2023-03-16 04:13:45 -07:00 committed by John Wu
parent 4e2b88b3d0
commit 76405bd984
2 changed files with 9 additions and 0 deletions
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5
native/src/core/bootstages.cpp
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@ -62,6 +62,11 @@ static void mount_mirrors() {
// Check and mount preinit mirror
if (struct stat st{}; stat((MAGISKTMP + "/" PREINITDEV).data(), &st) == 0 && (st.st_mode & S_IFBLK)) {
// DO NOT mount the block device directly, as we do not know the flags and configs
// to properly mount the partition; mounting block devices directly as rw could cause
// crashes if the filesystem driver is crap (e.g. some broken F2FS drivers).
// What we do instead is to scan through the current mountinfo and find a pre-existing
// mount point mounting our desired partition, and then bind mount the target folder.
dev_t preinit_dev = st.st_rdev;
for (const auto &info: self_mount_info) {
if (info.root == "/" && info.device == preinit_dev) {

4
native/src/init/mount.cpp
View File

@ -129,6 +129,10 @@ static void mount_preinit_dir(string path, dev_t preinit_dev) {
}
}
// Since we are mounting the block device directly, make sure to ONLY mount the partitions
// as read-only, or else the kernel might crash due to crappy drivers.
// After the device boots up, magiskd will properly bind mount the correct partition
// on to PREINITMIRR as writable. For more details, check bootstages.cpp
if (mounted || mount(PREINITDEV, PREINITMNT, "ext4", MS_RDONLY, nullptr) == 0 ||
mount(PREINITDEV, PREINITMNT, "f2fs", MS_RDONLY, nullptr) == 0) {
string preinit_dir = resolve_preinit_dir(PREINITMNT);