2022-10-19 03:34:55

by Zheng Wang

Subject: [PATCH v3] misc: sgi-gru: fix use-after-free error in gru_set_context_option, gru_fault and gru_handle_user_call_os

Gts may be freed in gru_check_chiplet_assignment.
The caller still use it after that, UAF happens.

Fix it by introducing a return value to see if it's in error path or not.
Free the gts in caller if gru_check_chiplet_assignment check failed.

Fixes: 55484c45dbec ("gru: allow users to specify gru chiplet 2")
Reported-by: Zheng Wang <[email protected]>
Signed-off-by: Zheng Wang <[email protected]>
---
v4:
- use VM_FAULT_NOPAGE as failure code in gru_fault and -EINVAL in other functions suggested by Yejian

v3:
- add preempt_enable and use VM_FAULT_NOPAGE as failure code suggested by Yejian

v2:
- commit message changes suggested by Greg

v1: https://lore.kernel.org/lkml/CAJedcCzY72jqgF-pCPtx66vXXwdPn-KMagZnqrxcpWw1NxTLaA@mail.gmail.com/
---
drivers/misc/sgi-gru/grufault.c | 14 ++++++++++++--
drivers/misc/sgi-gru/grumain.c | 18 ++++++++++++++----
drivers/misc/sgi-gru/grutables.h | 2 +-
3 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c
index d7ef61e602ed..2b5b049fbd38 100644
--- a/drivers/misc/sgi-gru/grufault.c
+++ b/drivers/misc/sgi-gru/grufault.c
@@ -656,7 +656,9 @@ int gru_handle_user_call_os(unsigned long cb)
if (ucbnum >= gts->ts_cbr_au_count * GRU_CBR_AU_SIZE)
goto exit;

- gru_check_context_placement(gts);
+ ret = gru_check_context_placement(gts);
+ if (ret)
+ goto err;

/*
* CCH may contain stale data if ts_force_cch_reload is set.
@@ -677,6 +679,10 @@ int gru_handle_user_call_os(unsigned long cb)
exit:
gru_unlock_gts(gts);
return ret;
+err:
+ gru_unlock_gts(gts);
+ gru_unload_context(gts, 1);
+ return -EINVAL;
}

/*
@@ -874,7 +880,7 @@ int gru_set_context_option(unsigned long arg)
} else {
gts->ts_user_blade_id = req.val1;
gts->ts_user_chiplet_id = req.val0;
- gru_check_context_placement(gts);
+ ret = gru_check_context_placement(gts);
}
break;
case sco_gseg_owner:
@@ -889,6 +895,10 @@ int gru_set_context_option(unsigned long arg)
ret = -EINVAL;
}
gru_unlock_gts(gts);
+ if (ret) {
+ gru_unload_context(gts, 1);
+ ret = -EINVAL;
+ }

return ret;
}
diff --git a/drivers/misc/sgi-gru/grumain.c b/drivers/misc/sgi-gru/grumain.c
index 9afda47efbf2..77becb52f550 100644
--- a/drivers/misc/sgi-gru/grumain.c
+++ b/drivers/misc/sgi-gru/grumain.c
@@ -716,9 +716,10 @@ static int gru_check_chiplet_assignment(struct gru_state *gru,
* chiplet. Misassignment can occur if the process migrates to a different
* blade or if the user changes the selected blade/chiplet.
*/
-void gru_check_context_placement(struct gru_thread_state *gts)
+int gru_check_context_placement(struct gru_thread_state *gts)
{
struct gru_state *gru;
+ int ret = 0;

/*
* If the current task is the context owner, verify that the
@@ -727,14 +728,16 @@ void gru_check_context_placement(struct gru_thread_state *gts)
*/
gru = gts->ts_gru;
if (!gru || gts->ts_tgid_owner != current->tgid)
- return;
+ return ret;

if (!gru_check_chiplet_assignment(gru, gts)) {
STAT(check_context_unload);
- gru_unload_context(gts, 1);
+ ret = -EINVAL;
} else if (gru_retarget_intr(gts)) {
STAT(check_context_retarget_intr);
}
+
+ return ret;
}


@@ -919,6 +922,7 @@ vm_fault_t gru_fault(struct vm_fault *vmf)
struct gru_thread_state *gts;
unsigned long paddr, vaddr;
unsigned long expires;
+ int ret;

vaddr = vmf->address;
gru_dbg(grudev, "vma %p, vaddr 0x%lx (0x%lx)\n",
@@ -934,7 +938,13 @@ vm_fault_t gru_fault(struct vm_fault *vmf)
mutex_lock(&gts->ts_ctxlock);
preempt_disable();

- gru_check_context_placement(gts);
+ ret = gru_check_context_placement(gts);
+ if (ret) {
+ preempt_enable();
+ mutex_unlock(&gts->ts_ctxlock);
+ gru_unload_context(gts, 1);
+ return VM_FAULT_NOPAGE;
+ }

if (!gts->ts_gru) {
STAT(load_user_context);
diff --git a/drivers/misc/sgi-gru/grutables.h b/drivers/misc/sgi-gru/grutables.h
index 5efc869fe59a..f4a5a787685f 100644
--- a/drivers/misc/sgi-gru/grutables.h
+++ b/drivers/misc/sgi-gru/grutables.h
@@ -632,7 +632,7 @@ extern int gru_user_flush_tlb(unsigned long arg);
extern int gru_user_unload_context(unsigned long arg);
extern int gru_get_exception_detail(unsigned long arg);
extern int gru_set_context_option(unsigned long address);
-extern void gru_check_context_placement(struct gru_thread_state *gts);
+extern int gru_check_context_placement(struct gru_thread_state *gts);
extern int gru_cpu_fault_map_id(void);
extern struct vm_area_struct *gru_find_vma(unsigned long vaddr);
extern void gru_flush_all_tlb(struct gru_state *gru);
--
2.25.1