If we hit an error path in GEM obj creation before msm_gem_new_handle()
updates obj->resv to point to the gpuvm resv object, then obj->resv
still points to &obj->_resv. In this case we don't want to decrement
the refcount of the object being freed (since the refcnt is already
zero). This fixes the following splat:
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 9 PID: 7013 at lib/refcount.c:28
refcount_warn_saturate+0xf4/0x148
Modules linked in: uinput snd_seq_dummy snd_hrtimer aes_ce_ccm
snd_soc_wsa884x regmap_sdw q6prm_clocks q6apm_lpass_da>
qcom_pil_info i2c_hid drm_kms_helper qcom_common qcom_q6v5 phy_snps_eusb2
qcom_geni_serial drm qcom_sysmon pinctrl_s>
CPU: 9 UID: 1000 PID: 7013 Comm: deqp-vk Not tainted 6.16.0-rc4-debug+ #25
PREEMPT(voluntary)
Hardware name: LENOVO 83ED/LNVNB161216, BIOS NHCN53WW 08/02/2024
pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
pc : refcount_warn_saturate+0xf4/0x148
lr : refcount_warn_saturate+0xf4/0x148
sp : ffff8000a2073920
x29: ffff8000a2073920 x28: 0000000000000010 x27: 0000000000000010
x26: 0000000000000042 x25: ffff000810e09800 x24: 0000000000000010
x23: ffff8000a2073b94 x22: ffff000ddb22de00 x21: ffff000ddb22dc00
x20: ffff000ddb22ddf8 x19: ffff0008024934e0 x18: 000000000000000a
x17: 0000000000000000 x16: ffff9f8c67d77340 x15: 0000000000000000
x14: 00000000ffffffff x13: 2e656572662d7265 x12: 7466612d65737520
x11: 3b776f6c66726564 x10: 00000000ffff7fff x9 : ffff9f8c67506c70
x8 : ffff9f8c69fa26f0 x7 : 00000000000bffe8 x6 : c0000000ffff7fff
x5 : ffff000f53e14548 x4 : ffff6082ea2b2000 x3 : ffff0008b86ab080
x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0008b86ab080
Call trace:
refcount_warn_saturate+0xf4/0x148 (P)
msm_gem_free_object+0x248/0x260 [msm]
drm_gem_object_free+0x24/0x40 [drm]
msm_gem_new+0x1c4/0x1e0 [msm]
msm_gem_new_handle+0x3c/0x1a0 [msm]
msm_ioctl_gem_new+0x38/0x70 [msm]
drm_ioctl_kernel+0xc8/0x138 [drm]
drm_ioctl+0x2c8/0x618 [drm]
__arm64_sys_ioctl+0xac/0x108
invoke_syscall.constprop.0+0x64/0xe8
el0_svc_common.constprop.0+0x40/0xe8
do_el0_svc+0x24/0x38
el0_svc+0x54/0x1d8
el0t_64_sync_handler+0x10c/0x138
el0t_64_sync+0x19c/0x1a0
irq event stamp: 3698694
hardirqs last enabled at (3698693): [<ffff9f8c675021dc>]
__up_console_sem+0x74/0x90
hardirqs last disabled at (3698694): [<ffff9f8c68ce8164>] el1_dbg+0x24/0x90
softirqs last enabled at (3697578): [<ffff9f8c6744ec5c>]
handle_softirqs+0x454/0x4b0
softirqs last disabled at (3697567): [<ffff9f8c67360244>]
__do_softirq+0x1c/0x28
---[ end trace 0000000000000000 ]---
Fixes: b58e12a66e47 ("drm/msm: Add _NO_SHARE flag")
Signed-off-by: Rob Clark <robin.cl...@oss.qualcomm.com>
---
drivers/gpu/drm/msm/msm_gem.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 33d3354c6102..958bac4e2768 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -1114,10 +1114,12 @@ static void msm_gem_free_object(struct drm_gem_object
*obj)
put_pages(obj);
}
- if (msm_obj->flags & MSM_BO_NO_SHARE) {
+ if (obj->resv != &obj->_resv) {
struct drm_gem_object *r_obj =
container_of(obj->resv, struct drm_gem_object, _resv);
+ WARN_ON(!(msm_obj->flags & MSM_BO_NO_SHARE));
+
/* Drop reference we hold to shared resv obj: */
drm_gem_object_put(r_obj);
}
--
2.50.1
