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Commit cf94fe15 authored by Jeff Sharkey's avatar Jeff Sharkey
Browse files

Offer a stricter way to prepare directories. 

Some callers, such as installd, have stricter requirements around
directory preparation, where they want to assert ownership and mode
without quietly fixing the values.

Bug: 26466827
Change-Id: Id44db5f29a3326cfe178b443fb450ad2edeaefd8
parent ba01a146

include/cutils/fs.h

+8 −1
Original line number Diff line number Diff line
@@ -40,10 +40,17 @@ extern "C" { 
#endif



/*

 * Ensure that directory exists with given mode and owners.

 * Ensure that directory exists with given mode and owners.  If it exists

 * with a different mode or owners, they are fixed to match the given values.

 */

extern int fs_prepare_dir(const char* path, mode_t mode, uid_t uid, gid_t gid);



/*

 * Ensure that directory exists with given mode and owners.  If it exists

 * with a different mode or owners, they are not fixed and -1 is returned.

 */

extern int fs_prepare_dir_strict(const char* path, mode_t mode, uid_t uid, gid_t gid);



/*

 * Read single plaintext integer from given file, correctly handling files

 * partially written with fs_write_atomic_int().

libcutils/fs.c

+14 −2
Original line number Diff line number Diff line
@@ -37,7 +37,8 @@ 
#define ALL_PERMS (S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)

#define BUF_SIZE 64



int fs_prepare_dir(const char* path, mode_t mode, uid_t uid, gid_t gid) {

static int fs_prepare_dir_impl(const char* path, mode_t mode, uid_t uid, gid_t gid,

        int allow_fixup) {

    // Check if path needs to be created

    struct stat sb;

    if (TEMP_FAILURE_RETRY(lstat(path, &sb)) == -1) {
@@ -56,8 +57,11 @@ int fs_prepare_dir(const char* path, mode_t mode, uid_t uid, gid_t gid) { 
    }

    if (((sb.st_mode & ALL_PERMS) == mode) && (sb.st_uid == uid) && (sb.st_gid == gid)) {

        return 0;

    } else {

    } else if (allow_fixup) {

        goto fixup;

    } else {

        ALOGE("Path %s exists with unexpected permissions", path);

        return -1;

    }



create:
@@ -81,6 +85,14 @@ fixup: 
    return 0;

}



int fs_prepare_dir(const char* path, mode_t mode, uid_t uid, gid_t gid) {

    return fs_prepare_dir_impl(path, mode, uid, gid, 1);

}



int fs_prepare_dir_strict(const char* path, mode_t mode, uid_t uid, gid_t gid) {

    return fs_prepare_dir_impl(path, mode, uid, gid, 0);

}



int fs_read_atomic_int(const char* path, int* out_value) {

    int fd = TEMP_FAILURE_RETRY(open(path, O_RDONLY));

    if (fd == -1) {