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Subject[PATCH] efi_64: Fix a missing-check bug in arch/x86/platform/efi/efi_64.c of Linux 5.1
save_pgd is allocated by kmalloc_array. And it is dereferenced in the
following codes. However, memory allocation functions such as
kmalloc_array may fail. Dereferencing this save_pgd null pointer may
cause the kernel go wrong. Thus we should check this allocation and add
error handling code.

Signed-off-by: Gen Zhang <blackgod016574@gmail.com>

---
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index cf0347f..fb9ae57 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -91,6 +91,8 @@ pgd_t * __init efi_call_phys_prolog(void)

n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT), PGDIR_SIZE);
save_pgd = kmalloc_array(n_pgds, sizeof(*save_pgd), GFP_KERNEL);
+ if (!save_pgd)
+ goto err;

/*
* Build 1:1 identity mapping for efi=old_map usage. Note that
@@ -142,6 +144,9 @@ pgd_t * __init efi_call_phys_prolog(void)
__flush_tlb_all();

return save_pgd;
+err:
+ __flush_tlb_all();
+ return ERR_PTR(-ENOMEM);
}

void __init efi_call_phys_epilog(pgd_t *save_pgd)
---
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