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btrfs-progs: utils: make sure set_label_mounted uses correct length buffers

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When `btrfs filesystem label /foo bar` command is invoked, it will pass
the buffer allocated in the argv array directly to set_label_mounted()
and then to the BTRFS_IOC_SET_FSLABEL ioctl.

However, the kernel code handling the ioctl will always try to copy
BTRFS_LABEL_SIZE bytes[1] from the userland pointer. Under certain
conditions and when the label is small enough, the command will fail
with:

    [root@localhost /]# btrfs filesystem label /mnt f
    ERROR: unable to set label Bad address

Fix this by making sure we pass a BTRFS_LABEL_SIZE sized buffer to the
ioctl containing the desired label.

[1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/btrfs/ioctl.c?id=refs/tags/v4.5#n5231

Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Petros Angelatos 2016-03-22 03:40:29 -07:00 committed by David Sterba
parent 90104b2618
commit ee78a83b5e
1 changed files with 4 additions and 1 deletions
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5
utils.c
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@ -1755,9 +1755,10 @@ static int set_label_unmounted(const char *dev, const char *label)
return 0;
}
static int set_label_mounted(const char *mount_path, const char *label)
static int set_label_mounted(const char *mount_path, const char *labelp)
{
int fd;
char label[BTRFS_LABEL_SIZE];
fd = open(mount_path, O_RDONLY | O_NOATIME);
if (fd < 0) {
@ -1765,6 +1766,8 @@ static int set_label_mounted(const char *mount_path, const char *label)
return -1;
}
memset(label, 0, sizeof(label));
strncpy(label, labelp, sizeof(label));
if (ioctl(fd, BTRFS_IOC_SET_FSLABEL, label) < 0) {
fprintf(stderr, "ERROR: unable to set label %s\n",
strerror(errno));