From: Borislav Petkov bp@suse.de

mainline inclusion from mainline-v5.6-rc3 commit 6e5cf31fbe651bed7ba1df768f2e123531132417 category: bugfix bugzilla: 189381 CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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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: 019f34fccfd5 ("x86, MCE, AMD: Move shared bank to node descriptor") Reported-by: Saar Amar Saar.Amar@microsoft.com Reported-by: Dan Carpenter dan.carpenter@oracle.com Signed-off-by: Borislav Petkov bp@suse.de Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20200128140846.phctkvx5btiexvbx@kili.mountain Signed-off-by: liwei liwei728@huawei.com --- arch/x86/kernel/cpu/mce/amd.c | 33 ++++++++++++++++----------------- 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c index 38b18fa055ef..af4a83695970 100644 --- a/arch/x86/kernel/cpu/mce/amd.c +++ b/arch/x86/kernel/cpu/mce/amd.c @@ -1200,8 +1200,9 @@ 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; @@ -1245,16 +1246,12 @@ 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: @@ -1262,7 +1259,7 @@ static int allocate_threshold_blocks(unsigned int cpu, unsigned int bank, 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;

@@ -1347,8 +1344,6 @@ 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);

@@ -1359,9 +1354,13 @@ 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);