diff options
author | Libor Pechacek <lpechacek@suse.cz> | 2020-01-31 14:28:29 +0100 |
---|---|---|
committer | Michael Ellerman <mpe@ellerman.id.au> | 2020-02-19 22:46:11 +1100 |
commit | a83836dbc53e96f13fec248ecc201d18e1e3111d (patch) | |
tree | 912994f1ac48e11735e3edebf068e0be92a93a5d /arch/powerpc/platforms/pseries/hotplug-memory.c | |
parent | c06f0aff035ed5a7eaff5daa8e11e7ad28ab0d54 (diff) |
powerpc/pseries: Avoid NULL pointer dereference when drmem is unavailable
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
Diffstat (limited to 'arch/powerpc/platforms/pseries/hotplug-memory.c')
-rw-r--r-- | arch/powerpc/platforms/pseries/hotplug-memory.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c index a4d40a3ceea3..fd22ec41c008 100644 --- 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, int n_lmbs, 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, int n_lmbs, 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; |