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Subject[tip:x86/urgent] x86/hyperv: Prevent potential NULL pointer dereference
Commit-ID:  534c89c22e26b183d838294f0937ee092c82ad3a
Gitweb: https://git.kernel.org/tip/534c89c22e26b183d838294f0937ee092c82ad3a
Author: Kangjie Lu <kjlu@umn.edu>
AuthorDate: Thu, 14 Mar 2019 00:46:51 -0500
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 21 Mar 2019 12:24:39 +0100

x86/hyperv: Prevent potential NULL pointer dereference

The page allocation in hv_cpu_init() can fail, but the code does not
have a check for that.

Add a check and return -ENOMEM when the allocation fails.

[ tglx: Massaged changelog ]

Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Acked-by: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: pakki001@umn.edu
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux-hyperv@vger.kernel.org
Link: https://lkml.kernel.org/r/20190314054651.1315-1-kjlu@umn.edu

---
arch/x86/hyperv/hv_init.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 6461a16b4559..e4ba467a9fc6 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -103,9 +103,13 @@ static int hv_cpu_init(unsigned int cpu)
u64 msr_vp_index;
struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
void **input_arg;
+ struct page *pg;

input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
- *input_arg = page_address(alloc_page(GFP_KERNEL));
+ pg = alloc_page(GFP_KERNEL);
+ if (unlikely(!pg))
+ return -ENOMEM;
+ *input_arg = page_address(pg);

hv_get_vp_index(msr_vp_index);

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