The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 6e5cf31fbe651bed7ba1df768f2e123531132417 Mon Sep 17 00:00:00 2001
From: Borislav Petkov bp@suse.de Date: Tue, 4 Feb 2020 13:28:41 +0100 Subject: [PATCH] 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: 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
diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c index b3a50d962851..e7313e5c497c 100644 --- a/arch/x86/kernel/cpu/mce/amd.c +++ b/arch/x86/kernel/cpu/mce/amd.c @@ -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 @@ 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;
@@ -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);