Re: SMB 1.0 broken between Kernel versions 6.2 and 6.5

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, Feb 15, 2024 at 1:02 PM Steve French <smfrench@xxxxxxxxx> wrote:
>
> Minor update to patch to work around the folios/netfs data corruption.
>
> In addition to printing the warning if "wsize=" is specified on mount
> with a size that is not a multiple of PAGE_SIZE, it also rounds the
> wsize down to the nearest multiple of PAGE_SIZE (as it was already
> doing if the server tried to negotiate a wsize that was not a multiple
> of PAGE_SIZE).
>
> On Fri, Feb 9, 2024 at 2:25 PM Steve French <smfrench@xxxxxxxxx> wrote:
> >
> > > > If the user does set their own "wsize", any value that is not a multiple of
> > > PAGE_SIZE is dangerous right?
> >
> > Yes for kernels 6.3 through 6.8-rc such a write size (ie that is not a
> > multiple of page size) can
> > be dangerous - that is why I added the warning on mount if the user
> > specifies the
> > potentially problematic wsize, since the wsize specified on mount
> > unlike the server
> > negotiated maximum write size is under the user's control.  The server
> > negotiated
> > maximum write size can't be controlled by the user, so for this
> > temporary fix we are
> > forced to round it down.   The actually bug is due to a folios/netfs
> > bug that David or
> > one of the mm experts may be able to spot (and fix) so for this
> > temporary workaround
> > I wanted to do the smaller change here so we don't have to revert it
> > later. I got close to
> > finding the actual bug (where the offset was getting reset, rounded up
> > incorrectly
> > inside one of the folios routines mentioned earlier in the thread) but
> > wanted to get something
> >
> > On Fri, Feb 9, 2024 at 2:51 AM Matthew Ruffell
> > <matthew.ruffell@xxxxxxxxxxxxx> wrote:
> > >
> > > Hi Steve,
> > >
> > > Yes, I am specifying "wsize" on the mount in my example, as its a little easier
> > > to reproduce the issue that way.
> > >
> > > If the user does set their own "wsize", any value that is not a multiple of
> > > PAGE_SIZE is dangerous right? Shouldn't we prevent the user from corrupting
> > > their data (un)intentionally if they happen to specify a wrong value? Especially
> > > since we know about it now. I know there haven't been any other reports in the
> > > year or so between 6.3 and present day, so there probably isn't any users out
> > > there actually setting their own "wsize", but it still feels bad to allow users
> > > to expose themselves to data corruption in this form.
> > >
> > > Please consider also rounding down "wsize" set on mount command line to a safe
> > > multiple of PAGE_SIZE. The code will only be around until David's netfslib cut
> > > over is merged anyway.
> > >
> > > I built a distro kernel and sent it to R. Diez for testing, so hopefully we will
> > > have some testing performed against an actual SMB server that sends a dangerous
> > > wsize during negotiation. I'll let you know how that goes, or R. Diez, you can
> > > tell us about how it goes here.
> > >
> > > Thanks,
> > > Matthew
> > >
> > > On Fri, 9 Feb 2024 at 18:38, Steve French <smfrench@xxxxxxxxx> wrote:
> > > >
> > > > Are you specifying "wsize" on the mount in your example?  The intent
> > > > of the patch is to warn the user using a non-recommended wsize (since
> > > > the user can control and fix that) but to force round_down when the
> > > > server sends a dangerous wsize (ie one that is not a multiple of
> > > > 4096).
> > > >
> > > > On Thu, Feb 8, 2024 at 3:31 AM Matthew Ruffell
> > > > <matthew.ruffell@xxxxxxxxxxxxx> wrote:
> > > > >
> > > > > Hi Steve,
> > > > >
> > > > > I built your latest patch ontop of 6.8-rc3, but the problem still persists.
> > > > >
> > > > > Looking at dmesg, I see the debug statement from the second hunk, but not from
> > > > > the first hunk, so I don't believe that wsize was ever rounded down to
> > > > > PAGE_SIZE.
> > > > >
> > > > > [  541.918267] Use of the less secure dialect vers=1.0 is not
> > > > > recommended unless required for access to very old servers
> > > > > [  541.920913] CIFS: VFS: Use of the less secure dialect vers=1.0 is
> > > > > not recommended unless required for access to very old servers
> > > > > [  541.923533] CIFS: VFS: wsize should be a multiple of 4096 (PAGE_SIZE)
> > > > > [  541.924755] CIFS: Attempting to mount //192.168.122.172/sambashare
> > > > >
> > > > > $ sha256sum sambashare/testdata.txt
> > > > > 9e573a0aa795f9cd4de4ac684a1c056dbc7d2ba5494d02e71b6225ff5f0fd866
> > > > > sambashare/testdata.txt
> > > > > $ less sambashare/testdata.txt
> > > > > ...
> > > > > 8dc8da96f7e5de0f312a2dbcc3c5c6facbfcc2fc206e29283274582ec93daa2a1496ca8edd49e3c1
> > > > > 6b^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^
> > > > > ...
> > > > >
> > > > > Would you be able compile and test your patch and see if we enter the logic from
> > > > > the first hunk?
> > > > >
> > > > > I'll be happy to test a V2 tomorrow.
> > > > >
> > > > > Thanks,
> > > > > Matthew
> > > > >
> > > > > On Thu, 8 Feb 2024 at 03:50, Steve French <smfrench@xxxxxxxxx> wrote:
> > > > > >
> > > > > > I had attached the wrong file - reattaching the correct patch (ie that
> > > > > > updates the previous version to use PAGE_SIZE instead of 4096)
> > > > > >
> > > > > > On Wed, Feb 7, 2024 at 1:12 AM Steve French <smfrench@xxxxxxxxx> wrote:
> > > > > > >
> > > > > > > Updated patch - now use PAGE_SIZE instead of hard coding to 4096.
> > > > > > >
> > > > > > > See attached
> > > > > > >
> > > > > > > On Tue, Feb 6, 2024 at 11:32 PM Steve French <smfrench@xxxxxxxxx> wrote:
> > > > > > > >
> > > > > > > > Attached updated patch which also adds check to make sure max write
> > > > > > > > size is at least 4K
> > > > > > > >
> > > > > > > > On Tue, Feb 6, 2024 at 10:58 PM Steve French <smfrench@xxxxxxxxx> wrote:
> > > > > > > > >
> > > > > > > > > > his netfslib work looks like quite a big refactor. Is there any plans to land this in 6.8? Or will this be 6.9 / later?
> > > > > > > > >
> > > > > > > > > I don't object to putting them in 6.8 if there was additional review
> > > > > > > > > (it is quite large), but I expect there would be pushback, and am
> > > > > > > > > concerned that David's status update did still show some TODOs for
> > > > > > > > > that patch series.  I do plan to upload his most recent set to
> > > > > > > > > cifs-2.6.git for-next later in the week and target would be for
> > > > > > > > > merging the patch series would be 6.9-rc1 unless major issues were
> > > > > > > > > found in review or testing
> > > > > > > > >
> > > > > > > > > On Tue, Feb 6, 2024 at 9:42 PM Matthew Ruffell
> > > > > > > > > <matthew.ruffell@xxxxxxxxxxxxx> wrote:
> > > > > > > > > >
> > > > > > > > > > I have bisected the issue, and found the commit that introduces the problem:
> > > > > > > > > >
> > > > > > > > > > commit d08089f649a0cfb2099c8551ac47eef0cc23fdf2
> > > > > > > > > > Author: David Howells <dhowells@xxxxxxxxxx>
> > > > > > > > > > Date:   Mon Jan 24 21:13:24 2022 +0000
> > > > > > > > > > Subject: cifs: Change the I/O paths to use an iterator rather than a page list
> > > > > > > > > > Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d08089f649a0cfb2099c8551ac47eef0cc23fdf2
> > > > > > > > > >
> > > > > > > > > > $ git describe --contains d08089f649a0cfb2099c8551ac47eef0cc23fdf2
> > > > > > > > > > v6.3-rc1~136^2~7
> > > > > > > > > >
> > > > > > > > > > David, I also tried your cifs-netfs tree available here:
> > > > > > > > > >
> > > > > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=cifs-netfs
> > > > > > > > > >
> > > > > > > > > > This tree solves the issue. Specifically:
> > > > > > > > > >
> > > > > > > > > > commit 34efb2a814f1882ddb4a518c2e8a54db119fd0d8
> > > > > > > > > > Author: David Howells <dhowells@xxxxxxxxxx>
> > > > > > > > > > Date:   Fri Oct 6 18:29:59 2023 +0100
> > > > > > > > > > Subject: cifs: Cut over to using netfslib
> > > > > > > > > > Link: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit/?h=cifs-netfs&id=34efb2a814f1882ddb4a518c2e8a54db119fd0d8
> > > > > > > > > >
> > > > > > > > > > This netfslib work looks like quite a big refactor. Is there any plans to land this in 6.8? Or will this be 6.9 / later?
> > > > > > > > > >
> > > > > > > > > > Do you have any suggestions on how to fix this with a smaller delta in 6.3 -> 6.8-rc3 that the stable kernels can use?
> > > > > > > > > >
> > > > > > > > > > Thanks,
> > > > > > > > > > Matthew
> > > > > > > > >
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > --
> > > > > > > > > Thanks,
> > > > > > > > >
> > > > > > > > > Steve
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > --
> > > > > > > > Thanks,
> > > > > > > >
> > > > > > > > Steve
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > --
> > > > > > > Thanks,
> > > > > > >
> > > > > > > Steve
> > > > > >
> > > > > >
> > > > > >
> > > > > > --
> > > > > > Thanks,
> > > > > >
> > > > > > Steve
> > > >
> > > >
> > > >
> > > > --
> > > > Thanks,
> > > >
> > > > Steve
> >
> >
> >
> > --
> > Thanks,
> >
> > Steve
>
>
>
> --
> Thanks,
>
> Steve

Minor comments.
In smb3_fs_context_parse_param, we don't strictly need to use
round_down twice. We could use a modulo operation for the check.
Also, there's an unnecessary change in fs_context.h though.
Other than that, the patch looks good to me. RB

-- 
Regards,
Shyam





[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [NTFS 3]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [NTFS 3]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux