[PATCH v2] nvme: check for valid data from from nvme_identify_ns() before using it

[Ewan Milne]

On Mon, Nov 27, 2023 at 5:03 PM Keith Busch <kbusch at kernel.org> wrote:
>
> On Mon, Nov 27, 2023 at 03:56:57PM -0500, Ewan D. Milne wrote:
> > When scanning namespaces, it is possible to get valid data from the first
> > call to nvme_identify_ns() in nvme_alloc_ns(), but not from the second
> > call in nvme_update_ns_info_block().  In particular, if the NSID becomes
> > inactive between the two commands, a storage device may return a buffer
> > filled with zero as per 4.1.5.1.  In this case, we can get a kernel crash
> > due to a divide-by-zero in blk_stack_limits() because ns->lba_shift will
> > be set to zero.
> >
> > PID: 326      TASK: ffff95fec3cd8000  CPU: 29   COMMAND: "kworker/u98:10"
> >  #0 [ffffad8f8702f9e0] machine_kexec at ffffffff91c76ec7
> >  #1 [ffffad8f8702fa38] __crash_kexec at ffffffff91dea4fa
> >  #2 [ffffad8f8702faf8] crash_kexec at ffffffff91deb788
> >  #3 [ffffad8f8702fb00] oops_end at ffffffff91c2e4bb
> >  #4 [ffffad8f8702fb20] do_trap at ffffffff91c2a4ce
> >  #5 [ffffad8f8702fb70] do_error_trap at ffffffff91c2a595
> >  #6 [ffffad8f8702fbb0] exc_divide_error at ffffffff928506e6
> >  #7 [ffffad8f8702fbd0] asm_exc_divide_error at ffffffff92a00926
> >     [exception RIP: blk_stack_limits+434]
> >     RIP: ffffffff92191872  RSP: ffffad8f8702fc80  RFLAGS: 00010246
> >     RAX: 0000000000000000  RBX: ffff95efa0c91800  RCX: 0000000000000001
> >     RDX: 0000000000000000  RSI: 0000000000000001  RDI: 0000000000000001
> >     RBP: 00000000ffffffff   R8: ffff95fec7df35a8   R9: 0000000000000000
> >     R10: 0000000000000000  R11: 0000000000000001  R12: 0000000000000000
> >     R13: 0000000000000000  R14: 0000000000000000  R15: ffff95fed33c09a8
> >     ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
> >  #8 [ffffad8f8702fce0] nvme_update_ns_info_block at ffffffffc06d3533 [nvme_core]
> >  #9 [ffffad8f8702fd18] nvme_scan_ns at ffffffffc06d6fa7 [nvme_core]
> >
> > This happened when the check for valid data was moved out of nvme_identify_ns()
> > into one of the callers.  Fix this by checking in both callers.
> >
> > v2: call kfree() on nvme_id_ns struct in error path
> >
> > Fixes: 0dd6fff2aad4 ("nvme: bring back auto-removal of deleted namespaces during sequential scan")
> > Cc: stable at vger.kernel.org
> > Signed-off-by: Ewan D. Milne <emilne at redhat.com>
>
> Thanks, applied for nvme-6.7.
>
> Interestingly enough, I think this is the same as what was recently
> reported here:
>
>   https://bugzilla.kernel.org/show_bug.cgi?id=218186
>

Yes, from the stack trace and BZ comments it looks like it.

-Ewan