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authorMuchun Song <songmuchun@bytedance.com>2020-09-04 16:36:13 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-09-09 19:04:32 +0200
commit221ea9a3da9169dc3c9a364a5f938e215db6419e (patch)
tree32c9f3ef475df867941786ed48b7daa3439102af
parentc5927539f17dd0c15f5760003d25ad83c107e053 (diff)
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mm/hugetlb: fix a race between hugetlb sysctl handlers
commit 17743798d81238ab13050e8e2833699b54e15467 upstream. There is a race between the assignment of `table->data` and write value to the pointer of `table->data` in the __do_proc_doulongvec_minmax() on the other thread. CPU0: CPU1: proc_sys_write hugetlb_sysctl_handler proc_sys_call_handler hugetlb_sysctl_handler_common hugetlb_sysctl_handler table->data = &tmp; hugetlb_sysctl_handler_common table->data = &tmp; proc_doulongvec_minmax do_proc_doulongvec_minmax sysctl_head_finish __do_proc_doulongvec_minmax unuse_table i = table->data; *i = val; // corrupt CPU1's stack Fix this by duplicating the `table`, and only update the duplicate of it. And introduce a helper of proc_hugetlb_doulongvec_minmax() to simplify the code. The following oops was seen: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor instruction fetch in kernel mode #PF: error_code(0x0010) - not-present page Code: Bad RIP value. ... Call Trace: ? set_max_huge_pages+0x3da/0x4f0 ? alloc_pool_huge_page+0x150/0x150 ? proc_doulongvec_minmax+0x46/0x60 ? hugetlb_sysctl_handler_common+0x1c7/0x200 ? nr_hugepages_store+0x20/0x20 ? copy_fd_bitmaps+0x170/0x170 ? hugetlb_sysctl_handler+0x1e/0x20 ? proc_sys_call_handler+0x2f1/0x300 ? unregister_sysctl_table+0xb0/0xb0 ? __fd_install+0x78/0x100 ? proc_sys_write+0x14/0x20 ? __vfs_write+0x4d/0x90 ? vfs_write+0xef/0x240 ? ksys_write+0xc0/0x160 ? __ia32_sys_read+0x50/0x50 ? __close_fd+0x129/0x150 ? __x64_sys_write+0x43/0x50 ? do_syscall_64+0x6c/0x200 ? entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fixes: e5ff215941d5 ("hugetlb: multiple hstates for multiple page sizes") Signed-off-by: Muchun Song <songmuchun@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Andi Kleen <ak@linux.intel.com> Link: http://lkml.kernel.org/r/20200828031146.43035-1-songmuchun@bytedance.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--mm/hugetlb.c26
1 files changed, 20 insertions, 6 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8a5708f31aa0..27e49c5ec219 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2918,6 +2918,22 @@ static unsigned int cpuset_mems_nr(unsigned int *array)
}
#ifdef CONFIG_SYSCTL
+static int proc_hugetlb_doulongvec_minmax(struct ctl_table *table, int write,
+ void *buffer, size_t *length,
+ loff_t *ppos, unsigned long *out)
+{
+ struct ctl_table dup_table;
+
+ /*
+ * In order to avoid races with __do_proc_doulongvec_minmax(), we
+ * can duplicate the @table and alter the duplicate of it.
+ */
+ dup_table = *table;
+ dup_table.data = out;
+
+ return proc_doulongvec_minmax(&dup_table, write, buffer, length, ppos);
+}
+
static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
struct ctl_table *table, int write,
void __user *buffer, size_t *length, loff_t *ppos)
@@ -2929,9 +2945,8 @@ static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
if (!hugepages_supported())
return -EOPNOTSUPP;
- table->data = &tmp;
- table->maxlen = sizeof(unsigned long);
- ret = proc_doulongvec_minmax(table, write, buffer, length, ppos);
+ ret = proc_hugetlb_doulongvec_minmax(table, write, buffer, length, ppos,
+ &tmp);
if (ret)
goto out;
@@ -2975,9 +2990,8 @@ int hugetlb_overcommit_handler(struct ctl_table *table, int write,
if (write && hstate_is_gigantic(h))
return -EINVAL;
- table->data = &tmp;
- table->maxlen = sizeof(unsigned long);
- ret = proc_doulongvec_minmax(table, write, buffer, length, ppos);
+ ret = proc_hugetlb_doulongvec_minmax(table, write, buffer, length, ppos,
+ &tmp);
if (ret)
goto out;