27993365c0
commit a83836dbc53e96f13fec248ecc201d18e1e3111d upstream. In guests without hotplugagble memory drmem structure is only zero initialized. Trying to manipulate DLPAR parameters results in a crash. $ echo "memory add count 1" > /sys/kernel/dlpar Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries ... NIP: c0000000000ff294 LR: c0000000000ff248 CTR: 0000000000000000 REGS: c0000000fb9d3880 TRAP: 0300 Tainted: G E (5.5.0-rc6-2-default) MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 28242428 XER: 20000000 CFAR: c0000000009a6c10 DAR: 0000000000000010 DSISR: 40000000 IRQMASK: 0 ... NIP dlpar_memory+0x6e4/0xd00 LR dlpar_memory+0x698/0xd00 Call Trace: dlpar_memory+0x698/0xd00 (unreliable) handle_dlpar_errorlog+0xc0/0x190 dlpar_store+0x198/0x4a0 kobj_attr_store+0x30/0x50 sysfs_kf_write+0x64/0x90 kernfs_fop_write+0x1b0/0x290 __vfs_write+0x3c/0x70 vfs_write+0xd0/0x260 ksys_write+0xdc/0x130 system_call+0x5c/0x68 Taking closer look at the code, I can see that for_each_drmem_lmb is a macro expanding into `for (lmb = &drmem_info->lmbs[0]; lmb <= &drmem_info->lmbs[drmem_info->n_lmbs - 1]; lmb++)`. When drmem_info->lmbs is NULL, the loop would iterate through the whole address range if it weren't stopped by the NULL pointer dereference on the next line. This patch aligns for_each_drmem_lmb and for_each_drmem_lmb_in_range macro behavior with the common C semantics, where the end marker does not belong to the scanned range, and alters get_lmb_range() semantics. As a side effect, the wraparound observed in the crash is prevented. Fixes: 6c6ea53725b3 ("powerpc/mm: Separate ibm, dynamic-memory data from DT format") Cc: stable@vger.kernel.org # v4.16+ Signed-off-by: Libor Pechacek <lpechacek@suse.cz> Signed-off-by: Michal Suchanek <msuchanek@suse.de> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200131132829.10281-1-msuchanek@suse.de 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.