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Check for SELinux labelling errors

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It's essential that files created by vold get the correct SELinux
labels, so make sure to check for errors when setting them.

ENOENT (no label defined) is expected on some files such as
/mnt/appfuse/*, so allow ENOENT but log a DEBUG message.

This will help debug b/269567270.  This is not a fix for b/269567270.

Bug: 269567270
Test: Created user and checked SELinux labels of user's directories
Test: atest CtsBlobStoreHostTestCases
Change-Id: Ife005bdd896952653943c57336deb33456f7c5d8
This commit is contained in:
Eric Biggers 2023-03-01 20:08:59 +00:00
parent 545f0ab758
commit c7c4f5a902
3 changed files with 57 additions and 51 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

62
Utils.cpp
View file

@ -23,6 +23,7 @@
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/properties.h>
#include <android-base/scopeguard.h>
#include <android-base/stringprintf.h>
#include <android-base/strings.h>
#include <android-base/unique_fd.h>
@ -100,13 +101,21 @@ std::string GetFuseMountPathForUser(userid_t user_id, const std::string& relativ
status_t CreateDeviceNode(const std::string& path, dev_t dev) {
std::lock_guard<std::mutex> lock(kSecurityLock);
const char* cpath = path.c_str();
status_t res = 0;
auto clearfscreatecon = android::base::make_scope_guard([] { setfscreatecon(nullptr); });
auto secontext = std::unique_ptr<char, void (*)(char*)>(nullptr, freecon);
char* tmp_secontext;
char* secontext = nullptr;
if (sehandle) {
if (!selabel_lookup(sehandle, &secontext, cpath, S_IFBLK)) {
setfscreatecon(secontext);
if (selabel_lookup(sehandle, &tmp_secontext, cpath, S_IFBLK) == 0) {
secontext.reset(tmp_secontext);
if (setfscreatecon(secontext.get()) != 0) {
LOG(ERROR) << "Failed to setfscreatecon for device node " << path;
return -EINVAL;
}
} else if (errno == ENOENT) {
LOG(DEBUG) << "No selabel defined for device node " << path;
} else {
PLOG(ERROR) << "Failed to look up selabel for device node " << path;
return -errno;
}
mode_t mode = 0660 | S_IFBLK;
@ -114,16 +123,10 @@ status_t CreateDeviceNode(const std::string& path, dev_t dev) {
if (errno != EEXIST) {
PLOG(ERROR) << "Failed to create device node for " << major(dev) << ":" << minor(dev)
<< " at " << path;
res = -errno;
return -errno;
}
}
if (secontext) {
setfscreatecon(nullptr);
freecon(secontext);
}
return res;
return OK;
}
status_t DestroyDeviceNode(const std::string& path) {
@ -449,29 +452,26 @@ status_t PrepareDir(const std::string& path, mode_t mode, uid_t uid, gid_t gid,
unsigned int attrs) {
std::lock_guard<std::mutex> lock(kSecurityLock);
const char* cpath = path.c_str();
auto clearfscreatecon = android::base::make_scope_guard([] { setfscreatecon(nullptr); });
auto secontext = std::unique_ptr<char, void (*)(char*)>(nullptr, freecon);
char* tmp_secontext;
char* secontext = nullptr;
if (sehandle) {
if (!selabel_lookup(sehandle, &secontext, cpath, S_IFDIR)) {
setfscreatecon(secontext);
if (selabel_lookup(sehandle, &tmp_secontext, cpath, S_IFDIR) == 0) {
secontext.reset(tmp_secontext);
if (setfscreatecon(secontext.get()) != 0) {
LOG(ERROR) << "Failed to setfscreatecon for directory " << path;
return -EINVAL;
}
}
int res = fs_prepare_dir(cpath, mode, uid, gid);
if (secontext) {
setfscreatecon(nullptr);
freecon(secontext);
}
if (res) return -errno;
if (attrs) res = SetAttrs(path, attrs);
if (res == 0) {
return OK;
} else if (errno == ENOENT) {
LOG(DEBUG) << "No selabel defined for directory " << path;
} else {
PLOG(ERROR) << "Failed to look up selabel for directory " << path;
return -errno;
}
if (fs_prepare_dir(cpath, mode, uid, gid) != 0) return -errno;
if (attrs && SetAttrs(path, attrs) != 0) return -errno;
return OK;
}
status_t ForceUnmount(const std::string& path) {

6
main.cpp
View file

@ -82,9 +82,11 @@ int main(int argc, char** argv) {
parse_args(argc, argv);
sehandle = selinux_android_file_context_handle();
if (sehandle) {
selinux_android_set_sehandle(sehandle);
if (!sehandle) {
LOG(ERROR) << "Failed to get SELinux file contexts handle";
exit(1);
}
selinux_android_set_sehandle(sehandle);
mkdir("/dev/block/vold", 0755);

22
vold_prepare_subdirs.cpp
View file

@ -58,32 +58,32 @@ static bool prepare_dir_for_user(struct selabel_handle* sehandle, mode_t mode, u
const std::string& path, uid_t user_id) {
auto clearfscreatecon = android::base::make_scope_guard([] { setfscreatecon(nullptr); });
auto secontext = std::unique_ptr<char, void (*)(char*)>(nullptr, freecon);
if (sehandle) {
char* tmp_secontext;
if (selabel_lookup(sehandle, &tmp_secontext, path.c_str(), S_IFDIR) == 0) {
secontext.reset(tmp_secontext);
if (user_id != (uid_t)-1) {
if (selinux_android_context_with_level(secontext.get(), &tmp_secontext, user_id,
(uid_t)-1) != 0) {
PLOG(ERROR) << "Unable to create context with level for: " << path;
return false;
}
secontext.reset(tmp_secontext); // Free the context
secontext.reset(tmp_secontext);
}
if (setfscreatecon(secontext.get()) != 0) {
LOG(ERROR) << "Failed to setfscreatecon for directory " << path;
return false;
}
} else if (errno == ENOENT) {
LOG(DEBUG) << "No selabel defined for directory " << path;
} else {
PLOG(ERROR) << "Failed to look up selabel for directory " << path;
return false;
}
LOG(DEBUG) << "Setting up mode " << std::oct << mode << std::dec << " uid " << uid << " gid "
<< gid << " context " << (secontext ? secontext.get() : "null")
<< " on path: " << path;
if (secontext) {
if (setfscreatecon(secontext.get()) != 0) {
PLOG(ERROR) << "Unable to setfscreatecon for: " << path;
return false;
}
}
if (fs_prepare_dir(path.c_str(), mode, uid, gid) != 0) {
return false;
}
@ -168,6 +168,10 @@ static bool prepare_apex_subdirs(struct selabel_handle* sehandle, const std::str
static bool prepare_subdirs(const std::string& volume_uuid, int user_id, int flags) {
struct selabel_handle* sehandle = selinux_android_file_context_handle();
if (!sehandle) {
LOG(ERROR) << "Failed to get SELinux file contexts handle";
return false;
}
if (flags & android::os::IVold::STORAGE_FLAG_DE) {
auto user_de_path = android::vold::BuildDataUserDePath(volume_uuid, user_id);