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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
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@ebiggers
ebiggers committed Mar 1, 2023
1 parent 545f0ab commit c7c4f5a
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Showing 3 changed files with 60 additions and 54 deletions.
66 changes: 33 additions & 33 deletions Utils.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand Down Expand Up @@ -100,30 +101,32 @@ 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;

char* secontext = nullptr;
if (sehandle) {
if (!selabel_lookup(sehandle, &secontext, cpath, S_IFBLK)) {
setfscreatecon(secontext);
auto clearfscreatecon = android::base::make_scope_guard([] { setfscreatecon(nullptr); });
auto secontext = std::unique_ptr<char, void (*)(char*)>(nullptr, freecon);
char* tmp_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;
if (mknod(cpath, mode, dev) < 0) {
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) {
Expand Down Expand Up @@ -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();

char* secontext = nullptr;
if (sehandle) {
if (!selabel_lookup(sehandle, &secontext, cpath, S_IFDIR)) {
setfscreatecon(secontext);
auto clearfscreatecon = android::base::make_scope_guard([] { setfscreatecon(nullptr); });
auto secontext = std::unique_ptr<char, void (*)(char*)>(nullptr, freecon);
char* tmp_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) {
Expand Down
6 changes: 4 additions & 2 deletions main.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);

Expand Down
42 changes: 23 additions & 19 deletions vold_prepare_subdirs.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
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);
}
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;
}
Expand Down Expand Up @@ -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);
Expand Down

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