Messages in this thread | | | Date | Mon, 7 Jan 2019 14:23:21 -0700 | From | Lina Iyer <> | Subject | Re: [PATCH] soc: qcom: rpmh: Avoid accessing freed memory from batch API |
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On Fri, Jan 04 2019 at 14:02 -0700, Evan Green wrote: >On Thu, Jan 3, 2019 at 9:47 AM Stephen Boyd <swboyd@chromium.org> wrote: >> >> Using the batch API from the interconnect driver sometimes leads to a >> KASAN error due to an access to freed memory. This is easier to trigger >> with threadirqs on the kernel commandline. >> >> BUG: KASAN: use-after-free in rpmh_tx_done+0x114/0x12c >> Read of size 1 at addr fffffff51414ad84 by task irq/110-apps_rs/57 >> >> CPU: 0 PID: 57 Comm: irq/110-apps_rs Tainted: G W 4.19.10 #72 >> Call trace: >> dump_backtrace+0x0/0x2f8 >> show_stack+0x20/0x2c >> __dump_stack+0x20/0x28 >> dump_stack+0xcc/0x10c >> print_address_description+0x74/0x240 >> kasan_report+0x250/0x26c >> __asan_report_load1_noabort+0x20/0x2c >> rpmh_tx_done+0x114/0x12c >> tcs_tx_done+0x450/0x768 >> irq_forced_thread_fn+0x58/0x9c >> irq_thread+0x120/0x1dc >> kthread+0x248/0x260 >> ret_from_fork+0x10/0x18 >> >> Allocated by task 385: >> kasan_kmalloc+0xac/0x148 >> __kmalloc+0x170/0x1e4 >> rpmh_write_batch+0x174/0x540 >> qcom_icc_set+0x8dc/0x9ac >> icc_set+0x288/0x2e8 >> a6xx_gmu_stop+0x320/0x3c0 >> a6xx_pm_suspend+0x108/0x124 >> adreno_suspend+0x50/0x60 >> pm_generic_runtime_suspend+0x60/0x78 >> __rpm_callback+0x214/0x32c >> rpm_callback+0x54/0x184 >> rpm_suspend+0x3f8/0xa90 >> pm_runtime_work+0xb4/0x178 >> process_one_work+0x544/0xbc0 >> worker_thread+0x514/0x7d0 >> kthread+0x248/0x260 >> ret_from_fork+0x10/0x18 >> >> Freed by task 385: >> __kasan_slab_free+0x12c/0x1e0 >> kasan_slab_free+0x10/0x1c >> kfree+0x134/0x588 >> rpmh_write_batch+0x49c/0x540 >> qcom_icc_set+0x8dc/0x9ac >> icc_set+0x288/0x2e8 >> a6xx_gmu_stop+0x320/0x3c0 >> a6xx_pm_suspend+0x108/0x124 >> adreno_suspend+0x50/0x60 >> cr50_spi spi5.0: SPI transfer timed out >> pm_generic_runtime_suspend+0x60/0x78 >> __rpm_callback+0x214/0x32c >> rpm_callback+0x54/0x184 >> rpm_suspend+0x3f8/0xa90 >> pm_runtime_work+0xb4/0x178 >> process_one_work+0x544/0xbc0 >> worker_thread+0x514/0x7d0 >> kthread+0x248/0x260 >> ret_from_fork+0x10/0x18 >> >> The buggy address belongs to the object at fffffff51414ac80 >> which belongs to the cache kmalloc-512 of size 512 >> The buggy address is located 260 bytes inside of >> 512-byte region [fffffff51414ac80, fffffff51414ae80) >> The buggy address belongs to the page: >> page:ffffffbfd4505200 count:1 mapcount:0 mapping:fffffff51e00c680 index:0x0 compound_mapcount: 0 >> flags: 0x4000000000008100(slab|head) >> raw: 4000000000008100 ffffffbfd4529008 ffffffbfd44f9208 fffffff51e00c680 >> raw: 0000000000000000 0000000000200020 00000001ffffffff 0000000000000000 >> page dumped because: kasan: bad access detected >> >> Memory state around the buggy address: >> fffffff51414ac80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> fffffff51414ad00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> >fffffff51414ad80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ^ >> fffffff51414ae00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> fffffff51414ae80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> >> The batch API sets the same completion for each rpmh message that's sent >> and then loops through all the messages and waits for that single >> completion declared on the stack to be completed before returning from >> the function and freeing the message structures. Unfortunately, some >> messages may still be in process and 'stuck' in the TCS. At some later >> point, the tcs_tx_done() interrupt will run and try to process messages >> that have already been freed at the end of rpmh_write_batch(). This will >> in turn access the 'needs_free' member of the rpmh_request structure and >> cause KASAN to complain. >> >> Let's fix this by allocating a chunk of completions for each message and >> waiting for all of them to be completed before returning from the batch >> API. Alternatively, we could wait for the last message in the batch, but >> that may be a more complicated change because it looks like >> tcs_tx_done() just iterates through the indices of the queue and >> completes each message instead of tracking the last inserted message and >> completing that first. >> >> Cc: Lina Iyer <ilina@codeaurora.org> >> Cc: "Raju P.L.S.S.S.N" <rplsssn@codeaurora.org> >> Cc: Matthias Kaehlcke <mka@chromium.org> >> Cc: Evan Green <evgreen@chromium.org> >> Fixes: c8790cb6da58 ("drivers: qcom: rpmh: add support for batch RPMH request") >> Signed-off-by: Stephen Boyd <swboyd@chromium.org> >> --- >> drivers/soc/qcom/rpmh.c | 25 +++++++++++++++++-------- >> 1 file changed, 17 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c >> index c7beb6841289..3b3e8b0b2d95 100644 >> --- a/drivers/soc/qcom/rpmh.c >> +++ b/drivers/soc/qcom/rpmh.c >> @@ -348,11 +348,12 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state, >> { >> struct batch_cache_req *req; >> struct rpmh_request *rpm_msgs; >> - DECLARE_COMPLETION_ONSTACK(compl); >> + struct completion *compls; >> struct rpmh_ctrlr *ctrlr = get_rpmh_ctrlr(dev); >> unsigned long time_left; >> int count = 0; >> int ret, i, j; >> + void *ptr; >> >> if (!cmd || !n) >> return -EINVAL; >> @@ -362,10 +363,15 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state, >> if (!count) >> return -EINVAL; >> >> - req = kzalloc(sizeof(*req) + count * sizeof(req->rpm_msgs[0]), >> + ptr = kzalloc(sizeof(*req) + >> + count * (sizeof(req->rpm_msgs[0]) + sizeof(*compls)), >> GFP_ATOMIC); >> - if (!req) >> + if (!ptr) >> return -ENOMEM; >> + >> + req = ptr; >> + compls = ptr + sizeof(*req) + count * sizeof(*rpm_msgs); >> + >> req->count = count; >> rpm_msgs = req->rpm_msgs; >> >> @@ -380,7 +386,10 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state, >> } >> >> for (i = 0; i < count; i++) { >> - rpm_msgs[i].completion = &compl; >> + struct completion *compl = &compls[i]; >> + >> + init_completion(compl); >> + rpm_msgs[i].completion = compl; >> ret = rpmh_rsc_send_data(ctrlr_to_drv(ctrlr), &rpm_msgs[i].msg); >> if (ret) { >> pr_err("Error(%d) sending RPMH message addr=%#x\n", > >It's a little weird that we call rpmh_tx_done on a bunch of transfers >we never submitted, just so the completion will get signaled so we can >wait on it in the next loop. We could just do count = i; break; here >instead. > It seems like it was carried over from my earlier submissions, where I was reference counting the number of completions for a batch. I beleive, with what we are doing here, we don't need to call tx_done with this approach.
>> @@ -393,12 +402,12 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state, >> >> time_left = RPMH_TIMEOUT_MS; >> for (i = 0; i < count; i++) { >> - time_left = wait_for_completion_timeout(&compl, time_left); >> + time_left = wait_for_completion_timeout(&compls[i], time_left); > >So we give RPMH_TIMEOUT_MS for all the completions to finish. I wonder >if it would be better to have that as RPMH_TIMEOUT_MS per completion. > That would work too. RPMH_TIMEOUT_MS is a large number that it should not be a problem with this approach either.
Thanks, Lina
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