Commit 314aec4a authored by Stefan Hajnoczi's avatar Stefan Hajnoczi Committed by Eduardo Habkost
Browse files

hostmem-file: reject invalid pmem file sizes 

Guests started with NVDIMMs larger than the underlying host file produce
confusing errors inside the guest.  This happens because the guest
accesses pages beyond the end of the file.

Check the pmem file size on startup and print a clear error message if
the size is invalid.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1669053


Cc: Wei Yang <richardw.yang@linux.intel.com>
Cc: Zhang Yi <yi.z.zhang@linux.intel.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20190214031004.32522-3-stefanha@redhat.com>
Reviewed-by: default avatarWei Yang <richardw.yang@linux.intel.com>
Reviewed-by: default avatarIgor Mammedov <imammedo@redhat.com>
Reviewed-by: default avatarPankaj Gupta <pagupta@redhat.com>
Signed-off-by: default avatarEduardo Habkost <ehabkost@redhat.com>
parent 336cfef4

backends/hostmem-file.c

+23 −0
Original line number Diff line number Diff line
@@ -56,6 +56,29 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) 
        error_setg(errp, "mem-path property not set");

        return;

    }



    /*

     * Verify pmem file size since starting a guest with an incorrect size

     * leads to confusing failures inside the guest.

     */

    if (fb->is_pmem) {

        Error *local_err = NULL;

        uint64_t size;



        size = qemu_get_pmem_size(fb->mem_path, &local_err);

        if (!size) {

            error_propagate(errp, local_err);

            return;

        }



        if (backend->size > size) {

            error_setg(errp, "size property %" PRIu64 " is larger than "

                       "pmem file \"%s\" size %" PRIu64, backend->size,

                       fb->mem_path, size);

            return;

        }

    }



    backend->force_prealloc = mem_prealloc;

    name = host_memory_backend_get_name(backend);

    memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),

include/qemu/osdep.h

+13 −0
Original line number Diff line number Diff line
@@ -570,6 +570,19 @@ void qemu_set_tty_echo(int fd, bool echo); 
void os_mem_prealloc(int fd, char *area, size_t sz, int smp_cpus,

                     Error **errp);



/**

 * qemu_get_pmem_size:

 * @filename: path to a pmem file

 * @errp: pointer to a NULL-initialized error object

 *

 * Determine the size of a persistent memory file.  Besides supporting files on

 * DAX file systems, this function also supports Linux devdax character

 * devices.

 *

 * Returns: the size or 0 on failure

 */

uint64_t qemu_get_pmem_size(const char *filename, Error **errp);



/**

 * qemu_get_pid_name:

 * @pid: pid of a process

util/oslib-posix.c

+53 −0
Original line number Diff line number Diff line
@@ -500,6 +500,59 @@ void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus, 
    }

}



uint64_t qemu_get_pmem_size(const char *filename, Error **errp)

{

    struct stat st;



    if (stat(filename, &st) < 0) {

        error_setg(errp, "unable to stat pmem file \"%s\"", filename);

        return 0;

    }



#if defined(__linux__)

    /* Special handling for devdax character devices */

    if (S_ISCHR(st.st_mode)) {

        char *subsystem_path = NULL;

        char *subsystem = NULL;

        char *size_path = NULL;

        char *size_str = NULL;

        uint64_t ret = 0;



        subsystem_path = g_strdup_printf("/sys/dev/char/%d:%d/subsystem",

                                         major(st.st_rdev), minor(st.st_rdev));

        subsystem = g_file_read_link(subsystem_path, NULL);

        if (!subsystem) {

            error_setg(errp, "unable to read subsystem for pmem file \"%s\"",

                       filename);

            goto devdax_err;

        }



        if (!g_str_has_suffix(subsystem, "/dax")) {

            error_setg(errp, "pmem file \"%s\" is not a dax device", filename);

            goto devdax_err;

        }



        size_path = g_strdup_printf("/sys/dev/char/%d:%d/size",

                                    major(st.st_rdev), minor(st.st_rdev));

        if (!g_file_get_contents(size_path, &size_str, NULL, NULL)) {

            error_setg(errp, "unable to read size for pmem file \"%s\"",

                       size_path);

            goto devdax_err;

        }



        ret = g_ascii_strtoull(size_str, NULL, 0);



devdax_err:

        g_free(size_str);

        g_free(size_path);

        g_free(subsystem);

        g_free(subsystem_path);

        return ret;

    }

#endif /* defined(__linux__) */



    return st.st_size;

}



char *qemu_get_pid_name(pid_t pid)

{

util/oslib-win32.c

+5 −0
Original line number Diff line number Diff line
@@ -560,6 +560,11 @@ void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus, 
    }

}



uint64_t qemu_get_pmem_size(const char *filename, Error **errp)

{

    error_setg(errp, "pmem support not available");

    return 0;

}



char *qemu_get_pid_name(pid_t pid)

{