On Mon, Jul 2, 2018 at 1:55 PM, tomas <tomasbortoli@xxxxxxxxx> wrote: > Yes, thanks. Please use my full name, Tomas Bortoli. Please also include: Reported-by: syzbot+60c837b428dc84e83a93@xxxxxxxxxxxxxxxxxxxxxxxxx from the original bug report. This this help to keep automatic testing process running. Thanks > > On 07/02/2018 12:20 PM, Ian Kent wrote: >> 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; >>> > > -- > You received this message because you are subscribed to the Google Groups "syzkaller" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe@xxxxxxxxxxxxxxxx. > For more options, visit https://groups.google.com/d/optout. -- To unsubscribe from this list: send the line "unsubscribe autofs" in
