linux-kernel - [PATCH] Coredump: fix crash when set core_pipe

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Message-Id: <20220314093705.5895-1-chaop.peng@gmail.com>
Date:   Mon, 14 Mar 2022 17:37:05 +0800
From:   "chao.peng" <chaop.peng@...il.com>
To:     viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     peng_super@....com, chaop.peng@...il.com
Subject: [PATCH] Coredump: fix crash when set core_pipe_limit

From: "chaop.peng" <chaop.peng@...il.com>

If core_pipe_count was set by /proc/sys/kernel/core_pipe_limit, and the
umh kernel config with the following configuration:
...
CONFIG_STATIC_USERMODEHELPER=y
CONFIG_STATIC_USERMODEHELPER_PATH=""
...
The umh was disabled and call_usermodehelper_exec() return early,
the variable core_pipe_limitand ispipe both with none-zero value,
if the current task signal is pending, call wait_for_dump_helpers
(cprm.file) with NULL value would caused carsh.

[26083.547473] Unable to handle kernel NULL pointer dereference at
virtual address 00000000000000d8
[26083.547485] Mem abort info:
[26083.547491]	 ESR = 0x96000006
[26083.547498]   EC = 0x25: DABT (current EL), IL = 32 bits
[26083.547504]	 SET = 0, FnV = 0
[26083.547509]	 EA = 0, S1PTW = 0
[26083.547514] Data abort info:
[26083.547520]	 ISV = 0, ISS = 0x00000006
[26083.547525]	 CM = 0, WnR = 0
[26083.547533] user pgtable: 4k pages, 39-bit VAs, pgdp=000000011181b000
[26083.547539] [00000000000000d8] pgd=0000000123e4e003
[26083.547543] , p4d=0000000123e4e003
[26083.547549] , pud=0000000123e4e003
[26083.547555] , pmd=0000000000000000
[26083.547570] Internal error: Oops: 96000006 [#1] PREEMPT SMP
[26083.597731] Kernel Offset: 0x1af0c0000 from 0xffffffc010000000
[26083.597744] PHYS_OFFSET: 0x40000000
[26083.597753] pstate: 22400005 (nzCv daif +PAN -UAO)
[26083.597765] pc : [0xffffffdb012a9280] do_coredump+0x99c/0x1ad4
[26083.597773] lr : [0xffffffdb012a90d0] do_coredump+0x7ec/0x1ad4
[26083.597778] sp : ffffffc048803b50
[26083.597784] x29: ffffffc048803c60 x28: ffffffdb03dee748
[26083.597790] x27: ffffff819060cec0 x26: ffffff8107a1f3c0
[26083.597796] x25: ffffff895e655400 x24: 0000000000000001
[26083.597801] x23: 0000000000000000 x22: 0000000000000000
[26083.597806] x21: ffffff818f3eb580 x20: ffffff81890973c0
[26083.597812] x19: ffffff800dff3780 x18: ffffffc03da8b020
[26083.597817] x17: ffffffdb03688544 x16: 0000000000000002
[26083.597823] x15: 0000000000000001 x14: 0000000000000000
[26083.597828] x13: ffffff818f3eb420 x12: 0000000000000000
[26083.597834] x11: 0000000000000001 x10: 0000000000000000
[26083.597839] x9 : 0000000000000000 x8 : 0000000000000000
[26083.597844] x7 : 0000000000000000 x6 : ffffff818f3eb428
[26083.597850] x5 : 0000000000000040 x4 : 0000000000000000
[26083.597855] x3 : 0000000000000001 x2 : 0000000000000001
[26083.597860] x1 : 0000000000000000 x0 : ffffff800fab8dc0
[26083.598835] Call trace:
[26083.598844]  dump_backtrace.cfi_jt+0x0/0x8
[26083.598852]  dump_stack_lvl+0xc4/0x140
[26083.598857]  dump_stack+0x1c/0x2c
[26083.598952]  die+0x344/0x748
[26083.598959]  die_kernel_fault+0x84/0x94
[26083.598965]  __do_kernel_fault+0x230/0x27c
[26083.598974]  do_page_fault+0xb4/0x778
[26083.598980]  do_translation_fault+0x48/0x64
[26083.598986]  do_mem_abort+0x6c/0x164
[26083.598993]  el1_abort+0x44/0x68
[26083.599000]  el1_sync_handler+0x58/0x88
[26083.599006]  el1_sync+0x8c/0x140
[26083.599013]  do_coredump+0x99c/0x1ad4
[26083.599020]  get_signal+0xc68/0xffc
[26083.599026]  do_signal+0xd4/0x268
[26083.599032]  do_notify_resume+0x15c/0x264
[26083.599038]  work_pending+0xc/0x5f0

Signed-off-by: chaop.peng <chaop.peng@...il.com>
---
 fs/coredump.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 1c060c0a2d72..7add39409203 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -736,15 +736,15 @@ void do_coredump(const kernel_siginfo_t *siginfo)
 	retval = unshare_files();
 	if (retval)
 		goto close_fail;
+	/*
+	 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
+	 * have this set to NULL.
+	 */
+	if (!cprm.file) {
+		pr_info("Core dump to |%s disabled\n", cn.corename);
+		goto close_fail;
+	}
 	if (!dump_interrupted()) {
-		/*
-		 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
-		 * have this set to NULL.
-		 */
-		if (!cprm.file) {
-			pr_info("Core dump to |%s disabled\n", cn.corename);
-			goto close_fail;
-		}
 		file_start_write(cprm.file);
 		core_dumped = binfmt->core_dump(&cprm);
 		/*
-- 
2.25.1