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authorCarlos Llamas <cmllamas@google.com>2022-11-05 02:12:35 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-11-09 17:41:27 +0300
commit3ce00bb7e91cf57d723905371507af57182c37ef (patch)
treecdf8653469264589c5b4f51350c0e8555ab14f33 /drivers/android/binder_alloc.c
parentab126f51c93a15093df604f661c9480854c005a3 (diff)
downloadlinux-3ce00bb7e91cf57d723905371507af57182c37ef.tar.xz
binder: validate alloc->mm in ->mmap() handler
Since commit 1da52815d5f1 ("binder: fix alloc->vma_vm_mm null-ptr dereference") binder caches a pointer to the current->mm during open(). This fixes a null-ptr dereference reported by syzkaller. Unfortunately, it also opens the door for a process to update its mm after the open(), (e.g. via execve) making the cached alloc->mm pointer invalid. Things get worse when the process continues to mmap() a vma. From this point forward, binder will attempt to find this vma using an obsolete alloc->mm reference. Such as in binder_update_page_range(), where the wrong vma is obtained via vma_lookup(), yet binder proceeds to happily insert new pages into it. To avoid this issue fail the ->mmap() callback if we detect a mismatch between the vma->vm_mm and the original alloc->mm pointer. This prevents alloc->vm_addr from getting set, so that any subsequent vma_lookup() calls fail as expected. Fixes: 1da52815d5f1 ("binder: fix alloc->vma_vm_mm null-ptr dereference") Reported-by: Jann Horn <jannh@google.com> Cc: <stable@vger.kernel.org> # 5.15+ Signed-off-by: Carlos Llamas <cmllamas@google.com> Acked-by: Todd Kjos <tkjos@google.com> Link: https://lore.kernel.org/r/20221104231235.348958-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/android/binder_alloc.c')
-rw-r--r--drivers/android/binder_alloc.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 1c39cfce32fa..4ad42b0f75cd 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -739,6 +739,12 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc,
const char *failure_string;
struct binder_buffer *buffer;
+ if (unlikely(vma->vm_mm != alloc->mm)) {
+ ret = -EINVAL;
+ failure_string = "invalid vma->vm_mm";
+ goto err_invalid_mm;
+ }
+
mutex_lock(&binder_alloc_mmap_lock);
if (alloc->buffer_size) {
ret = -EBUSY;
@@ -785,6 +791,7 @@ err_alloc_pages_failed:
alloc->buffer_size = 0;
err_already_mapped:
mutex_unlock(&binder_alloc_mmap_lock);
+err_invalid_mm:
binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
"%s: %d %lx-%lx %s failed %d\n", __func__,
alloc->pid, vma->vm_start, vma->vm_end,