CVE-2021-46927

In the Linux kernel, the following vulnerability has been resolved:

nitro_enclaves: Use get_user_pages_unlocked() call to handle mmap assert

After commit 5b78ed24e8ec ("mm/pagemap: add mmap_assert_locked() annotations to find_vma*()"), the call to get_user_pages() will trigger the mmap assert.

static inline void mmap_assert_locked(struct mm_struct *mm) { lockdep_assert_held(&mm->mmap_lock); VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm); }

[ 62.521410] kernel BUG at include/linux/mmap_lock.h:156! ........................................................... [ 62.538938] RIP: 0010:find_vma+0x32/0x80 ........................................................... [ 62.605889] Call Trace: [ 62.608502] <TASK> [ 62.610956] ? lock_timer_base+0x61/0x80 [ 62.614106] find_extend_vma+0x19/0x80 [ 62.617195] __get_user_pages+0x9b/0x6a0 [ 62.620356] __gup_longterm_locked+0x42d/0x450 [ 62.623721] ? finish_wait+0x41/0x80 [ 62.626748] ? __kmalloc+0x178/0x2f0 [ 62.629768] ne_set_user_memory_region_ioctl.isra.0+0x225/0x6a0 [nitro_enclaves] [ 62.635776] ne_enclave_ioctl+0x1cf/0x6d7 [nitro_enclaves] [ 62.639541] __x64_sys_ioctl+0x82/0xb0 [ 62.642620] do_syscall_64+0x3b/0x90 [ 62.645642] entry_SYSCALL_64_after_hwframe+0x44/0xae

Use get_user_pages_unlocked() when setting the enclave memory regions. That's a similar pattern as mmap_read_lock() used together with get_user_pages().

Red Hat Enterprise Linux 8 and 9 are not affected by this vulnerability.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.