From: Libor Pechacek <lpechacek@xxxxxxx>
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@xxxxxxxxxxxxxxx # v4.16+
Signed-off-by: Libor Pechacek <lpechacek@xxxxxxx>
Signed-off-by: Michal Suchanek <msuchanek@xxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20200131132829.10281-1-msuchanek@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/include/asm/drmem.h | 4 ++--
arch/powerpc/platforms/pseries/hotplug-memory.c | 8 ++++----
2 files changed, 6 insertions(+), 6 deletions(-)
--- a/arch/powerpc/include/asm/drmem.h
+++ b/arch/powerpc/include/asm/drmem.h
@@ -27,12 +27,12 @@ struct drmem_lmb_info {
extern struct drmem_lmb_info *drmem_info;
#define for_each_drmem_lmb_in_range(lmb, start, end) \
- for ((lmb) = (start); (lmb) <= (end); (lmb)++)
+ for ((lmb) = (start); (lmb) < (end); (lmb)++)
#define for_each_drmem_lmb(lmb) \
for_each_drmem_lmb_in_range((lmb), \
&drmem_info->lmbs[0], \
- &drmem_info->lmbs[drmem_info->n_lmbs - 1])
+ &drmem_info->lmbs[drmem_info->n_lmbs])
/*
* The of_drconf_cell_v1 struct defines the layout of the LMB data
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -223,7 +223,7 @@ static int get_lmb_range(u32 drc_index,
struct drmem_lmb **end_lmb)
{
struct drmem_lmb *lmb, *start, *end;
- struct drmem_lmb *last_lmb;
+ struct drmem_lmb *limit;
start = NULL;
for_each_drmem_lmb(lmb) {
@@ -236,10 +236,10 @@ static int get_lmb_range(u32 drc_index,
if (!start)
return -EINVAL;
- end = &start[n_lmbs - 1];
+ end = &start[n_lmbs];
- last_lmb = &drmem_info->lmbs[drmem_info->n_lmbs - 1];
- if (end > last_lmb)
+ limit = &drmem_info->lmbs[drmem_info->n_lmbs];
+ if (end > limit)
return -EINVAL;
*start_lmb = start;
