stat() completion successful and set wrong errno, when a component of the path prefix is not a directory [ext2, dummyfs, jffs2]

[mateusz-bloch]

stat() completion successful and set wrong errno, when a component of the path is existing regular file, not a directory

Tested between ia32-generic and host-generic

Code to reproduction:

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <errno.h>

int main(void)
{
    struct stat buf;

    FILE *fp = fopen("testfile.txt", "w");
    fclose(fp);

    errno = 0;
    stat("testfile.txt/", &buf);
    printf("Regular File: %d\n",S_ISREG(buf.st_mode));
    printf("Directory: %d\n",S_ISDIR(buf.st_mode));
    printf("Errno: %d, %s\n", errno, strerror(errno));

    remove("testfile.txt");

    return 0;
}

Outcome from ia32-generic:

Outcome from host-generic:

Documentation:

[nalajcie]

Please note that:

• when function exits with error, output parameter might be left unchanged - IMHO You shouldn't test it unless it's explicitly stated it's also set on error paths
• most of our FS-related functions are implemented inside particular filesystem - it's worth to check also how the function behaves on jffs2 and dummyfs (I believe it's possible to test on zynq-qemu as rootfs is jffs2 there and /dev is dummyfs ; currently it's not possible to test other FSes on ia32 due to phoenix-rtos/phoenix-rtos-project#114)
• due to above - please state on which filesystems the bug is present (preferably all fliesystems in single issue)

[jmaksymowicz]

I managed to track down the bug to the resolve_path function in libphoenix. According to Open Group it should set errno to ENOTDIR when:

[...] the file_name argument contains at least one non-\<slash> character and ends with one or more trailing \<slash> characters and the last pathname component names an existing file that is neither a directory nor a symbolic link to a directory.

Instead, the function simply ignores trailing slashes, so it cannot behave correctly.