On Mon, 2018-07-02 at 10:31 +0200, tomas wrote: > Hi Ian, > > you are welcome! > > yes your patch is much better. You should just put the "_IOC_NR" macro > around "cmd" in the lines added to "validate_dev_ioctl" to make it work. LOL, yes, that was a dumb mistake. I'll send it to Andrew Morton, after some fairly simple sanity testing, with both our Signed-off-by added. > > Tomas > > > On 07/02/2018 03:42 AM, Ian Kent wrote: > > On Mon, 2018-07-02 at 09:10 +0800, Ian Kent wrote: > > > On Mon, 2018-07-02 at 00:04 +0200, tomas wrote: > > > > Hi, > > > > > > > > I've looked into this issue found by Syzbot and I made a patch: > > > > > > > > https://syzkaller.appspot.com/bug?id=d03abd8b42847f7f69b1d1d7f97208ae425 > > > > b116 > > > > 3 > > > > > > Umm ... oops! > > > > > > Thanks for looking into this Tomas. > > > > > > > > > > > The autofs subsystem does not check that the "path" parameter is present > > > > within the "param" struct passed by the userspace in case the > > > > AUTOFS_DEV_IOCTL_OPENMOUNT_CMD command is passed. Indeed, it assumes a > > > > path is always provided (though a path is not always present, as per how > > > > the struct is defined: > > > > https://github.com/torvalds/linux/blob/master/include/uapi/linux/auto_de > > > > v-io > > > > ct > > > > l.h#L89). > > > > Skipping the check provokes an oob read in "strlen", called by > > > > "getname_kernel", in turn called by the autofs to assess the length of > > > > the non-existing path. > > > > > > > > To solve it, modify the "validate_dev_ioctl" function to check also that > > > > a path has been provided if the command is > > > > AUTOFS_DEV_IOCTL_OPENMOUNT_CMD. > > > > > > > > > > > > --- b/fs/autofs/dev-ioctl.c 2018-07-01 23:10:16.059728621 +0200around > > > > +++ a/fs/autofs/dev-ioctl.c 2018-07-01 23:10:24.311792133 +0200 > > > > @@ -136,6 +136,9 @@ static int validate_dev_ioctl(int cmd, s > > > > goto out; > > > > } > > > > } > > > > + /* AUTOFS_DEV_IOCTL_OPENMOUNT_CMD without path */ > > > > + else if(_IOC_NR(cmd) == AUTOFS_DEV_IOCTL_OPENMOUNT_CMD) > > > > + return -EINVAL; > > > > > > My preference is to put the comment inside the else but ... > > > > > > There's another question, should the check be done in > > > autofs_dev_ioctl_openmount() in the same way it's checked in other > > > ioctls that need a path, such as in autofs_dev_ioctl_requester() > > > and autofs_dev_ioctl_ismountpoint()? > > > > > > For consistency I'd say it should. > > > > > > > > > > > err = 0;You should just put the "_IOC_NR" directive around "cmd" in > > > > the lines added to "validate_dev_ioctl" to make it work. > > > > out: > > > > > > > > > > > > Tested and solves the issue on Linus' main git tree. > > > > > > > > > > > > Or perhaps this (not even compile tested) patch would be better? > > > > autofs - fix slab out of bounds read in getname_kernel() > > > > From: Ian Kent <raven@xxxxxxxxxx> > > > > The autofs subsystem does not check that the "path" parameter is > > present for all cases where it is required when it is passed in > > via the "param" struct. > > > > In particular it isn't checked for the AUTOFS_DEV_IOCTL_OPENMOUNT_CMD > > ioctl command. > > > > To solve it, modify validate_dev_ioctl() function to check that a > > path has been provided for ioctl commands that require it. > > --- > > fs/autofs/dev-ioctl.c | 15 +++++++-------- > > 1 file changed, 7 insertions(+), 8 deletions(-) > > > > diff --git a/fs/autofs/dev-ioctl.c b/fs/autofs/dev-ioctl.c > > index ea4ca1445ab7..61c63715c3fb 100644 > > --- a/fs/autofs/dev-ioctl.c > > +++ b/fs/autofs/dev-ioctl.c > > @@ -135,6 +135,11 @@ static int validate_dev_ioctl(int cmd, struct > > autofs_dev_ioctl *param) > > cmd); > > goto out; > > } > > + } else if (cmd == AUTOFS_DEV_IOCTL_OPENMOUNT_CMD || > > + cmd == AUTOFS_DEV_IOCTL_REQUESTER_CMD || > > + cmd == AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD) { > > + err = -EINVAL; > > + goto out; > > } > > > > err = 0; > > @@ -433,10 +438,7 @@ static int autofs_dev_ioctl_requester(struct file *fp, > > dev_t devid; > > int err = -ENOENT; > > > > - if (param->size <= AUTOFS_DEV_IOCTL_SIZE) { > > - err = -EINVAL; > > - goto out; > > - } > > + /* param->path has already been checked */ > > > > devid = sbi->sb->s_dev; > > > > @@ -521,10 +523,7 @@ static int autofs_dev_ioctl_ismountpoint(struct file > > *fp, > > unsigned int devid, magic; > > int err = -ENOENT; > > > > - if (param->size <= AUTOFS_DEV_IOCTL_SIZE) { > > - err = -EINVAL; > > - goto out; > > - } > > + /* param->path has already been checked */ > > > > name = param->path; > > type = param->ismountpoint.in.type; > > -- To unsubscribe from this list: send the line "unsubscribe autofs" in
