Subject: CVE-2024-41065: powerpc/pseries: Whitelist dtl slub object for copying to userspace

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

powerpc/pseries: Whitelist dtl slub object for copying to userspace

Reading the dispatch trace log from /sys/kernel/debug/powerpc/dtl/cpu-*
results in a BUG() when the config CONFIG_HARDENED_USERCOPY is enabled as
shown below.

    kernel BUG at mm/usercopy.c:102!
    Oops: Exception in kernel mode, sig: 5 [#1]
    LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
    Modules linked in: xfs libcrc32c dm_service_time sd_mod t10_pi sg ibmvfc
    scsi_transport_fc ibmveth pseries_wdt dm_multipath dm_mirror dm_region_hash dm_log dm_mod fuse
    CPU: 27 PID: 1815 Comm: python3 Not tainted 6.10.0-rc3 #85
    Hardware name: IBM,9040-MRX POWER10 (raw) 0x800200 0xf000006 of:IBM,FW1060.00 (NM1060_042) hv:phyp pSeries
    NIP:  c0000000005d23d4 LR: c0000000005d23d0 CTR: 00000000006ee6f8
    REGS: c000000120c078c0 TRAP: 0700   Not tainted  (6.10.0-rc3)
    MSR:  8000000000029033 <SF,EE,ME,IR,DR,RI,LE>  CR: 2828220f  XER: 0000000e
    CFAR: c0000000001fdc80 IRQMASK: 0
    [ ... GPRs omitted ... ]
    NIP [c0000000005d23d4] usercopy_abort+0x78/0xb0
    LR [c0000000005d23d0] usercopy_abort+0x74/0xb0
    Call Trace:
     usercopy_abort+0x74/0xb0 (unreliable)
     __check_heap_object+0xf8/0x120
     check_heap_object+0x218/0x240
     __check_object_size+0x84/0x1a4
     dtl_file_read+0x17c/0x2c4
     full_proxy_read+0x8c/0x110
     vfs_read+0xdc/0x3a0
     ksys_read+0x84/0x144
     system_call_exception+0x124/0x330
     system_call_vectored_common+0x15c/0x2ec
    --- interrupt: 3000 at 0x7fff81f3ab34

Commit 6d07d1cd300f ("usercopy: Restrict non-usercopy caches to size 0")
requires that only whitelisted areas in slab/slub objects can be copied to
userspace when usercopy hardening is enabled using CONFIG_HARDENED_USERCOPY.
Dtl contains hypervisor dispatch events which are expected to be read by
privileged users. Hence mark this safe for user access.
Specify useroffset=0 and usersize=DISPATCH_LOG_BYTES to whitelist the
entire object.

The Linux kernel CVE team has assigned CVE-2024-41065 to this issue.

Affected and fixed versions
===========================

	Fixed in 5.4.281 with commit a7b952941ce0
	Fixed in 5.10.223 with commit 6b16098148ea
	Fixed in 5.15.164 with commit e59822f9d700
	Fixed in 6.1.101 with commit 1ee68686d1e2
	Fixed in 6.6.42 with commit e512a59b4726
	Fixed in 6.9.11 with commit 0f5892212c27
	Fixed in 6.10 with commit 1a14150e1656

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-41065
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	arch/powerpc/platforms/pseries/setup.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/a7b952941ce07e1e7a2cafd08c64a98e14f553e6
	https://git.kernel.org/stable/c/6b16098148ea58a67430d90e20476be2377c3acd
	https://git.kernel.org/stable/c/e59822f9d700349cd17968d22c979db23a2d347f
	https://git.kernel.org/stable/c/1ee68686d1e2a5da35d5650be0be1ce06fe2ceb2
	https://git.kernel.org/stable/c/e512a59b472684d8585125101ab03b86c2c1348a
	https://git.kernel.org/stable/c/0f5892212c27be31792ef1daa89c8dac1b3047e4
	https://git.kernel.org/stable/c/1a14150e1656f7a332a943154fc486504db4d586