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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
	Wang ShaoBo <bobo.shaobowang@huawei.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH AUTOSEL 5.7 19/25] x86/stacktrace: Fix reliable check for empty user task stacks
Date: Mon, 27 Jul 2020 19:23:39 -0400	[thread overview]
Message-ID: <20200727232345.717432-19-sashal@kernel.org> (raw)
In-Reply-To: <20200727232345.717432-1-sashal@kernel.org>

From: Josh Poimboeuf <jpoimboe@redhat.com>

[ Upstream commit 039a7a30ec102ec866d382a66f87f6f7654f8140 ]

If a user task's stack is empty, or if it only has user regs, ORC
reports it as a reliable empty stack.  But arch_stack_walk_reliable()
incorrectly treats it as unreliable.

That happens because the only success path for user tasks is inside the
loop, which only iterates on non-empty stacks.  Generally, a user task
must end in a user regs frame, but an empty stack is an exception to
that rule.

Thanks to commit 71c95825289f ("x86/unwind/orc: Fix error handling in
__unwind_start()"), unwind_start() now sets state->error appropriately.
So now for both ORC and FP unwinders, unwind_done() and !unwind_error()
always means the end of the stack was successfully reached.  So the
success path for kthreads is no longer needed -- it can also be used for
empty user tasks.

Reported-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Link: https://lkml.kernel.org/r/f136a4e5f019219cbc4f4da33b30c2f44fa65b84.1594994374.git.jpoimboe@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kernel/stacktrace.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 6ad43fc44556e..2fd698e28e4d5 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -58,7 +58,6 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
 			 * or a page fault), which can make frame pointers
 			 * unreliable.
 			 */
-
 			if (IS_ENABLED(CONFIG_FRAME_POINTER))
 				return -EINVAL;
 		}
@@ -81,10 +80,6 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
 	if (unwind_error(&state))
 		return -EINVAL;
 
-	/* Success path for non-user tasks, i.e. kthreads and idle tasks */
-	if (!(task->flags & (PF_KTHREAD | PF_IDLE)))
-		return -EINVAL;
-
 	return 0;
 }
 
-- 
2.25.1


  parent reply	other threads:[~2020-07-27 23:29 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-27 23:23 [PATCH AUTOSEL 5.7 01/25] mt76: mt7615: fix lmac queue debugsfs entry Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 02/25] iwlwifi: fix crash in iwl_dbg_tlv_alloc_trigger Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 03/25] usb: hso: Fix debug compile warning on sparc32 Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 04/25] selftests: fib_nexthop_multiprefix: fix cleanup() netns deletion Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 05/25] qed: Disable "MFW indication via attention" SPAM every 5 minutes Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 06/25] selftests: net: ip_defrag: modprobe missing nf_defrag_ipv6 support Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 07/25] io_uring: always allow drain/link/hardlink/async sqe flags Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 08/25] habanalabs: prevent possible out-of-bounds array access Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 09/25] nfc: s3fwrn5: add missing release on skb in s3fwrn5_recv_frame Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 10/25] scsi: core: Run queue in case of I/O resource contention failure Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 11/25] riscv: kasan: use local_tlb_flush_all() to avoid uninitialized __sbi_rfence Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 12/25] parisc: add support for cmpxchg on u8 pointers Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 13/25] net: ethernet: ravb: exit if re-initialization fails in tx timeout Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 14/25] selftest: txtimestamp: fix net ns entry logic Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 15/25] drivers/net/wan/x25_asy: Fix to make it work Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 16/25] Revert "i2c: cadence: Fix the hold bit setting" Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 17/25] i2c: cadence: Clear HOLD bit at correct time in Rx path Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 18/25] x86/unwind/orc: Fix ORC for newly forked tasks Sasha Levin
2020-07-27 23:23 ` Sasha Levin [this message]
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 20/25] cxgb4: add missing release on skb in uld_send() Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 21/25] io_uring: missed req_init_async() for IOSQE_ASYNC Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 22/25] xen-netfront: fix potential deadlock in xennet_remove() Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 23/25] RISC-V: Set maximum number of mapped pages correctly Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 24/25] drivers/net/wan: lapb: Corrected the usage of skb_cow Sasha Levin
2020-07-27 23:23 ` [PATCH AUTOSEL 5.7 25/25] riscv: Parse all memory blocks to remove unusable memory Sasha Levin

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