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ANDROID: dma-buf: Add vendorhook to allow mmaping more memory than a DMA-BUF holds

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Add vendorhook to allow mmaping more memory than a DMA-BUF holds. The
implementor of the vmap callback for the DMA-BUF is responsible for
ensuring that all pages are backed by memory. The hook takes as input
a DMA-BUF to allow the VMA bounds check to be done on a case-by-case
basis for DMA-BUFs.

Note that if the override is allowed to go through for a given
DMA-BUF, then it can be the case that the size of this mmaped DMA-BUF
is reported incorrectly when looking at /proc/pid/maps for the owning
process.

Bug: 234753494
Change-Id: Iba8cc8adfd2290e4dc7ef04fce5d6a80ac92e0b3
Signed-off-by: Chris Goldsworthy <quic_cgoldswo@quicinc.com>
Signed-off-by: Sukadev Bhattiprolu <quic_sukadev@quicinc.com>
This commit is contained in:
Chris Goldsworthy 2022-07-27 16:58:09 -07:00 • committed by Sukadev Bhattiprolu
parent 41d708af25
commit 9972a4f7df
3 changed files with 30 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

3
drivers/android/vendor_hooks.c
View file

@ -7,6 +7,7 @@
*/
#include <linux/iova.h>
#include <linux/dma-buf.h>
#define CREATE_TRACE_POINTS
#include <trace/hooks/vendor_hooks.h>
@ -41,6 +42,7 @@
#include <trace/hooks/rwsem.h>
#include <trace/hooks/futex.h>
#include <trace/hooks/fips140.h>
#include <trace/hooks/dmabuf.h>
/*
* Export tracepoints that act as a bare tracehook (ie: have no trace event
@ -113,6 +115,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(android_rvh_selinux_is_initialized);
EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_check_mmap_file);
EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_check_file_open);
EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_check_bpf_syscall);
EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_ignore_dmabuf_vmap_bounds);
EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_rproc_recovery);
EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_rproc_recovery_set);
EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_rwsem_init);

8
drivers/dma-buf/dma-buf.c
View file

@ -27,6 +27,7 @@
#include <linux/mm.h>
#include <linux/mount.h>
#include <linux/pseudo_fs.h>
#include <trace/hooks/dmabuf.h>
#include <uapi/linux/dma-buf.h>
#include <uapi/linux/magic.h>
@ -130,6 +131,7 @@ static struct file_system_type dma_buf_fs_type = {
static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
{
struct dma_buf *dmabuf;
bool ignore_bounds = false;
if (!is_dma_buf_file(file))
return -EINVAL;
@ -140,9 +142,11 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
if (!dmabuf->ops->mmap)
return -EINVAL;
trace_android_vh_ignore_dmabuf_vmap_bounds(dmabuf, &ignore_bounds);
/* check for overflowing the buffer's size */
if (vma->vm_pgoff + vma_pages(vma) >
dmabuf->size >> PAGE_SHIFT)
if ((vma->vm_pgoff + vma_pages(vma) >
dmabuf->size >> PAGE_SHIFT) && !ignore_bounds)
return -EINVAL;
return dmabuf->ops->mmap(dmabuf, vma);

21
include/trace/hooks/dmabuf.h Normal file
View file

@ -0,0 +1,21 @@
/* SPDX-License-Identifier: GPL-2.0 */
#undef TRACE_SYSTEM
#define TRACE_SYSTEM dmabuf
#define TRACE_INCLUDE_PATH trace/hooks
#if !defined(_TRACE_HOOK_DMA_BUF_H) || defined(TRACE_HEADER_MULTI_READ)
#define _TRACE_HOOK_DMA_BUF_H
struct dma_buf;
#include <trace/hooks/vendor_hooks.h>
DECLARE_HOOK(android_vh_ignore_dmabuf_vmap_bounds,
TP_PROTO(struct dma_buf *dma_buf, bool *ignore_bounds),
TP_ARGS(dma_buf, ignore_bounds));
#endif /* _TRACE_HOOK_DMA_BUF_H */
/* This part must be outside protection */
#include <trace/define_trace.h>