1d29e21ed0
commit 4f3175979e62de3b929bfa54a0db4b87d36257a7 upstream. With hardened usercopy enabled (CONFIG_HARDENED_USERCOPY=y), using the /proc/powerpc/rtas/firmware_update interface to prepare a system firmware update yields a BUG(): kernel BUG at mm/usercopy.c:102! Oops: Exception in kernel mode, sig: 5 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries Modules linked in: CPU: 0 PID: 2232 Comm: dd Not tainted 6.5.0-rc3+ #2 Hardware name: IBM,8408-E8E POWER8E (raw) 0x4b0201 0xf000004 of:IBM,FW860.50 (SV860_146) hv:phyp pSeries NIP: c0000000005991d0 LR: c0000000005991cc CTR: 0000000000000000 REGS: c0000000148c76a0 TRAP: 0700 Not tainted (6.5.0-rc3+) MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE> CR: 24002242 XER: 0000000c CFAR: c0000000001fbd34 IRQMASK: 0 [ ... GPRs omitted ... ] NIP usercopy_abort+0xa0/0xb0 LR usercopy_abort+0x9c/0xb0 Call Trace: usercopy_abort+0x9c/0xb0 (unreliable) __check_heap_object+0x1b4/0x1d0 __check_object_size+0x2d0/0x380 rtas_flash_write+0xe4/0x250 proc_reg_write+0xfc/0x160 vfs_write+0xfc/0x4e0 ksys_write+0x90/0x160 system_call_exception+0x178/0x320 system_call_common+0x160/0x2c4 The blocks of the firmware image are copied directly from user memory to objects allocated from flash_block_cache, so flash_block_cache must be created using kmem_cache_create_usercopy() to mark it safe for user access. Fixes: 6d07d1cd300f ("usercopy: Restrict non-usercopy caches to size 0") Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> Reviewed-by: Kees Cook <keescook@chromium.org> [mpe: Trim and indent oops] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20230810-rtas-flash-vs-hardened-usercopy-v2-1-dcf63793a938@linux.ibm.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.