Subject: CVE-2024-35921: media: mediatek: vcodec: Fix oops when HEVC init fails

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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

media: mediatek: vcodec: Fix oops when HEVC init fails

The stateless HEVC decoder saves the instance pointer in the context
regardless if the initialization worked or not. This caused a use after
free, when the pointer is freed in case of a failure in the deinit
function.
Only store the instance pointer when the initialization was successful,
to solve this issue.

 Hardware name: Acer Tomato (rev3 - 4) board (DT)
 pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 pc : vcodec_vpu_send_msg+0x4c/0x190 [mtk_vcodec_dec]
 lr : vcodec_send_ap_ipi+0x78/0x170 [mtk_vcodec_dec]
 sp : ffff80008750bc20
 x29: ffff80008750bc20 x28: ffff1299f6d70000 x27: 0000000000000000
 x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
 x23: ffff80008750bc98 x22: 000000000000a003 x21: ffffd45c4cfae000
 x20: 0000000000000010 x19: ffff1299fd668310 x18: 000000000000001a
 x17: 000000040044ffff x16: ffffd45cb15dc648 x15: 0000000000000000
 x14: ffff1299c08da1c0 x13: ffffd45cb1f87a10 x12: ffffd45cb2f5fe80
 x11: 0000000000000001 x10: 0000000000001b30 x9 : ffffd45c4d12b488
 x8 : 1fffe25339380d81 x7 : 0000000000000001 x6 : ffff1299c9c06c00
 x5 : 0000000000000132 x4 : 0000000000000000 x3 : 0000000000000000
 x2 : 0000000000000010 x1 : ffff80008750bc98 x0 : 0000000000000000
 Call trace:
  vcodec_vpu_send_msg+0x4c/0x190 [mtk_vcodec_dec]
  vcodec_send_ap_ipi+0x78/0x170 [mtk_vcodec_dec]
  vpu_dec_deinit+0x1c/0x30 [mtk_vcodec_dec]
  vdec_hevc_slice_deinit+0x30/0x98 [mtk_vcodec_dec]
  vdec_if_deinit+0x38/0x68 [mtk_vcodec_dec]
  mtk_vcodec_dec_release+0x20/0x40 [mtk_vcodec_dec]
  fops_vcodec_release+0x64/0x118 [mtk_vcodec_dec]
  v4l2_release+0x7c/0x100
  __fput+0x80/0x2d8
  __fput_sync+0x58/0x70
  __arm64_sys_close+0x40/0x90
  invoke_syscall+0x50/0x128
  el0_svc_common.constprop.0+0x48/0xf0
  do_el0_svc+0x24/0x38
  el0_svc+0x38/0xd8
  el0t_64_sync_handler+0xc0/0xc8
  el0t_64_sync+0x1a8/0x1b0
 Code: d503201f f9401660 b900127f b900227f (f9400400)

The Linux kernel CVE team has assigned CVE-2024-35921 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 6.5 with commit 2674486aac7d and fixed in 6.6.27 with commit ec25fc3c2c1e
	Issue introduced in 6.5 with commit 2674486aac7d and fixed in 6.8.6 with commit 521ce0ea7418
	Issue introduced in 6.5 with commit 2674486aac7d and fixed in 6.9 with commit 97c75ee5de06

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-35921
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_hevc_req_multi_if.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/ec25fc3c2c1e8958a51abcfed614f81446d918c4
	https://git.kernel.org/stable/c/521ce0ea7418298d754494fe53263c23c4c78a8e
	https://git.kernel.org/stable/c/97c75ee5de060d271d80109b0c47cb6008439e5b