Commit 6e5cf31f authored by Borislav Petkov's avatar Borislav Petkov
Browse files

x86/mce/amd: Publish the bank pointer only after setup has succeeded 



threshold_create_bank() creates a bank descriptor per MCA error
thresholding counter which can be controlled over sysfs. It publishes
the pointer to that bank in a per-CPU variable and then goes on to
create additional thresholding blocks if the bank has such.

However, that creation of additional blocks in
allocate_threshold_blocks() can fail, leading to a use-after-free
through the per-CPU pointer.

Therefore, publish that pointer only after all blocks have been setup
successfully.

Fixes: 019f34fc ("x86, MCE, AMD: Move shared bank to node descriptor")
Reported-by: default avatarSaar Amar <Saar.Amar@microsoft.com>
Reported-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200128140846.phctkvx5btiexvbx@kili.mountain
parent bb6d3fb3

arch/x86/kernel/cpu/mce/amd.c

+16 −17
Original line number Diff line number Diff line
@@ -1198,8 +1198,9 @@ static const char *get_name(unsigned int bank, struct threshold_block *b) 
	return buf_mcatype;

}



static int allocate_threshold_blocks(unsigned int cpu, unsigned int bank,

				     unsigned int block, u32 address)

static int allocate_threshold_blocks(unsigned int cpu, struct threshold_bank *tb,

				     unsigned int bank, unsigned int block,

				     u32 address)

{

	struct threshold_block *b = NULL;

	u32 low, high;
@@ -1243,16 +1244,12 @@ static int allocate_threshold_blocks(unsigned int cpu, unsigned int bank, 


	INIT_LIST_HEAD(&b->miscj);



	if (per_cpu(threshold_banks, cpu)[bank]->blocks) {

		list_add(&b->miscj,

			 &per_cpu(threshold_banks, cpu)[bank]->blocks->miscj);

	} else {

		per_cpu(threshold_banks, cpu)[bank]->blocks = b;

	}

	if (tb->blocks)

		list_add(&b->miscj, &tb->blocks->miscj);

	else

		tb->blocks = b;



	err = kobject_init_and_add(&b->kobj, &threshold_ktype,

				   per_cpu(threshold_banks, cpu)[bank]->kobj,

				   get_name(bank, b));

	err = kobject_init_and_add(&b->kobj, &threshold_ktype, tb->kobj, get_name(bank, b));

	if (err)

		goto out_free;

recurse:
@@ -1260,7 +1257,7 @@ recurse: 
	if (!address)

		return 0;



	err = allocate_threshold_blocks(cpu, bank, block, address);

	err = allocate_threshold_blocks(cpu, tb, bank, block, address);

	if (err)

		goto out_free;
@@ -1345,8 +1342,6 @@ static int threshold_create_bank(unsigned int cpu, unsigned int bank) 
		goto out_free;

	}



	per_cpu(threshold_banks, cpu)[bank] = b;



	if (is_shared_bank(bank)) {

		refcount_set(&b->cpus, 1);
@@ -1357,9 +1352,13 @@ static int threshold_create_bank(unsigned int cpu, unsigned int bank) 
		}

	}



	err = allocate_threshold_blocks(cpu, bank, 0, msr_ops.misc(bank));

	if (!err)

		goto out;

	err = allocate_threshold_blocks(cpu, b, bank, 0, msr_ops.misc(bank));

	if (err)

		goto out_free;



	per_cpu(threshold_banks, cpu)[bank] = b;



	return 0;



 out_free:

	kfree(b);

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