[PATCH] powerpc/smp: Handle of_property_count_u32_elems() error in parse_thread_groups()

[PATCH] powerpc/smp: Handle of_property_count_u32_elems() error in parse_thread_groups()

[Nathan Chancellor]

After commit 0af298e62e5c ("treewide: refresh kmalloc_obj()
conversions"), there is a warning on boot for several PowerPC
configurations in QEMU:

  WARNING: mm/slub.c:5459 at ___kmalloc_large_node+0x174/0x1b0, CPU#0: swapper/0/1
  Modules linked in:
  CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.4.0-rc1-00262-g0af298e62e5c #1 PREEMPT(lazy)
  NIP [c0000000006074e4] ___kmalloc_large_node+0x174/0x1b0
  LR [c00000000060782c] __kmalloc_large_node_noprof+0x3c/0x150
  Call Trace:
  ...
  [c00000000369fb60] [c000000000614ff0] __kmalloc_noprof+0x490/0x690
  [c00000000369fbe0] [c000000000051308] _kzalloc_noprof.constprop.0+0x1c/0x74
  [c00000000369fc00] [c00000000200b450] init_thread_group_cache_map+0xc0/0x2c4
  ...

In this case, of_property_count_u32_elems() returns -EINVAL because
there is no "ibm,thread-groups" property. When kcalloc() was used to
allocate thread_group_array, the multiplication overflow check in
_kmalloc_array_noprof() caught that a really large allocation was
requested (as -EINVAL was converted to size_t) and returned NULL.
kzalloc_objs() has no such check, so the large allocation check in
__kmalloc_large_noprof() triggers the visible warning above.

Check if of_property_count_u32_elems() has returned an error and bail
out if so, clearing up the warning.

Fixes: 790a1662d3a2 ("powerpc/smp: Parse ibm,thread-groups with multiple properties")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 arch/powerpc/kernel/smp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 7a25eaa59e62..58824f5f4c80 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -824,6 +824,8 @@ static int parse_thread_groups(struct device_node *dn,
 	int i = 0;
 
 	count = of_property_count_u32_elems(dn, "ibm,thread-groups");
+	if (count < 0)
+		return count;
 	thread_group_array = kzalloc_objs(u32, count);
 	if (!thread_group_array)
 		return -ENOMEM;

---
base-commit: 7475ea8b58616b33c04afb976cf0fbaad9dd63fb
base-tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
change-id: 20261109-powerpc-smp-handle-count-err-b48b9ffd6e90

Best regards,
--  
Cheers,
Nathan