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[61.230.24.179]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a3e3cc7856sm136174865ad.68.2026.01.10.11.10.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 10 Jan 2026 11:10:30 -0800 (PST) Date: Sun, 11 Jan 2026 03:10:27 +0800 From: Kuan-Wei Chiu To: djakov@kernel.org Cc: quic_mdtipton@quicinc.com, mike.tipton@oss.qualcomm.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] interconnect: debugfs: initialize src_node and dst_node to empty strings Message-ID: References: <20260109122523.125843-1-djakov@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260109122523.125843-1-djakov@kernel.org> Hi Georgi, On Fri, Jan 09, 2026 at 02:25:23PM +0200, djakov@kernel.org wrote: > From: Georgi Djakov > > The debugfs_create_str() API assumes that the string pointer is either NULL > or points to valid kmalloc() memory. Leaving the pointer uninitialized can > cause problems. > > Initialize src_node and dst_node to empty strings before creating the > debugfs entries to guarantee that reads and writes are safe. > > Fixes: 770c69f037c1 ("interconnect: Add debugfs test client") > Signed-off-by: Georgi Djakov I verified this patch on qemu. Without this patch, reading the debugfs node triggers a NULL pointer dereference [1]. # cat /sys/kernel/debug/interconnect/test_client/src_node The patch resolves this issue. Thanks! Reviewed-by: Kuan-Wei Chiu Tested-by: Kuan-Wei Chiu Regards, Kuan-Wei [1]: [ 53.134642] traps: skippy[737] trap invalid opcode ip:7f125b62e967 sp:7fff26f593c0 error:0 in ld-2.27.so[25967,7f125b609000+2b000] [ 53.171664] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 53.172274] #PF: supervisor read access in kernel mode [ 53.172556] #PF: error_code(0x0000) - not-present page [ 53.173103] PGD 0 P4D 0 [ 53.173433] Oops: Oops: 0000 [#1] SMP NOPTI [ 53.176057] CPU: 51 UID: 0 PID: 738 Comm: cat Tainted: G N 6.19.0-rc4-virtme #2 PREEMPT(voluntary) [ 53.176747] Tainted: [N]=TEST [ 53.176964] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 53.177493] RIP: 0010:strlen+0x4/0x30 [ 53.178437] Code: f7 75 ec 31 c0 c3 cc cc cc cc 48 89 f8 c3 cc cc cc cc 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa <80> 3f 00 74 18 48 89 f8 0f 1f 40 00 48 83 c0 01 80 38 00 75 f7 48 [ 53.179507] RSP: 0018:ffffb279018ffe10 EFLAGS: 00010246 [ 53.179831] RAX: ffffffffba33cde0 RBX: 0000000000000000 RCX: 0000000000000002 [ 53.180215] RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000000 [ 53.180563] RBP: 0000000000000001 R08: ffffffffb9061ec0 R09: 0000000000000000 [ 53.181030] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000040000 [ 53.181366] R13: ffffb279018ffee8 R14: ffff8dcec5c30540 R15: 0000000000000000 [ 53.181803] FS: 00007f54fc097740(0000) GS:ffff8dcf4145f000(0000) knlGS:0000000000000000 [ 53.182251] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 53.182541] CR2: 0000000000000000 CR3: 000000000838d000 CR4: 00000000000006f0 [ 53.183078] Call Trace: [ 53.184925] [ 53.185202] debugfs_read_file_str+0x49/0xf0 [ 53.185961] vfs_read+0xc2/0x3a0 [ 53.186195] ? __hrtimer_run_queues+0x160/0x2a0 [ 53.186442] ? __pfx_read_tsc+0x10/0x10 [ 53.186634] ? ktime_get+0x3b/0xd0 [ 53.186974] ? lapic_next_event+0x15/0x20 [ 53.187147] ? clockevents_program_event+0x99/0xf0 [ 53.187374] ksys_read+0x6b/0xe0 [ 53.187563] do_syscall_64+0xa4/0xf80 [ 53.187867] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 53.188365] RIP: 0033:0x7f54fc129687 [ 53.189177] Code: 48 89 fa 4c 89 df e8 58 b3 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff [ 53.190393] RSP: 002b:00007ffde7e25960 EFLAGS: 00000202 ORIG_RAX: 0000000000000000 [ 53.190900] RAX: ffffffffffffffda RBX: 00007f54fc097740 RCX: 00007f54fc129687 [ 53.191488] RDX: 0000000000040000 RSI: 00007f54fc056000 RDI: 0000000000000003 [ 53.191963] RBP: 0000000000040000 R08: 0000000000000000 R09: 0000000000000000 [ 53.192351] R10: 0000000000000000 R11: 0000000000000202 R12: 00007f54fc056000 [ 53.192776] R13: 0000000000000003 R14: 0000000000000000 R15: 0000000000040000 [ 53.193345] [ 53.193572] Modules linked in: [ 53.194157] CR2: 0000000000000000 [ 53.195723] ---[ end trace 0000000000000000 ]--- [ 53.196335] RIP: 0010:strlen+0x4/0x30 [ 53.196556] Code: f7 75 ec 31 c0 c3 cc cc cc cc 48 89 f8 c3 cc cc cc cc 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa <80> 3f 00 74 18 48 89 f8 0f 1f 40 00 48 83 c0 01 80 38 00 75 f7 48 [ 53.197634] RSP: 0018:ffffb279018ffe10 EFLAGS: 00010246 [ 53.198037] RAX: ffffffffba33cde0 RBX: 0000000000000000 RCX: 0000000000000002 [ 53.198388] RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000000 [ 53.198793] RBP: 0000000000000001 R08: ffffffffb9061ec0 R09: 0000000000000000 [ 53.199193] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000040000 [ 53.199544] R13: ffffb279018ffee8 R14: ffff8dcec5c30540 R15: 0000000000000000 [ 53.199959] FS: 00007f54fc097740(0000) GS:ffff8dcf4145f000(0000) knlGS:0000000000000000 [ 53.200322] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 53.200615] CR2: 0000000000000000 CR3: 000000000838d000 CR4: 00000000000006f0 Killed cat src_node