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author | Todd Kjos <tkjos@android.com> | 2019-06-05 09:38:25 -0700 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-06-09 09:17:23 +0200 |
commit | 9d57cfd4e9d81400c1fe2b7cd4503f54830b46c2 (patch) | |
tree | b14e97e3f7dba91a64e65a7032e37e5e26e5eb8f | |
parent | 137c838f177b86797a9a805bb131e0f96cdac565 (diff) | |
download | linux-stable-9d57cfd4e9d81400c1fe2b7cd4503f54830b46c2.tar.gz linux-stable-9d57cfd4e9d81400c1fe2b7cd4503f54830b46c2.tar.bz2 linux-stable-9d57cfd4e9d81400c1fe2b7cd4503f54830b46c2.zip |
binder: fix race between munmap() and direct reclaim
commit 5cec2d2e5839f9c0fec319c523a911e0a7fd299f upstream.
An munmap() on a binder device causes binder_vma_close() to be called
which clears the alloc->vma pointer.
If direct reclaim causes binder_alloc_free_page() to be called, there
is a race where alloc->vma is read into a local vma pointer and then
used later after the mm->mmap_sem is acquired. This can result in
calling zap_page_range() with an invalid vma which manifests as a
use-after-free in zap_page_range().
The fix is to check alloc->vma after acquiring the mmap_sem (which we
were acquiring anyway) and skip zap_page_range() if it has changed
to NULL.
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Todd Kjos <tkjos@google.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: stable <stable@vger.kernel.org> # 4.19
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r-- | drivers/android/binder_alloc.c | 18 |
1 files changed, 8 insertions, 10 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 030c98f35cca..a654ccfd1a22 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -958,14 +958,13 @@ enum lru_status binder_alloc_free_page(struct list_head *item, index = page - alloc->pages; page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE; + + mm = alloc->vma_vm_mm; + if (!mmget_not_zero(mm)) + goto err_mmget; + if (!down_write_trylock(&mm->mmap_sem)) + goto err_down_write_mmap_sem_failed; vma = binder_alloc_get_vma(alloc); - if (vma) { - if (!mmget_not_zero(alloc->vma_vm_mm)) - goto err_mmget; - mm = alloc->vma_vm_mm; - if (!down_write_trylock(&mm->mmap_sem)) - goto err_down_write_mmap_sem_failed; - } list_lru_isolate(lru, item); spin_unlock(lock); @@ -978,10 +977,9 @@ enum lru_status binder_alloc_free_page(struct list_head *item, PAGE_SIZE); trace_binder_unmap_user_end(alloc, index); - - up_write(&mm->mmap_sem); - mmput(mm); } + up_write(&mm->mmap_sem); + mmput(mm); trace_binder_unmap_kernel_start(alloc, index); |