Messages in this thread Patch in this message | | | Subject | [PATCH] trace: fix null pointer dereference in tracing_err_log_open() | From | Mateusz Stachyra <> | Date | Mon, 03 Jul 2023 17:52:37 +0200 |
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From d6ef949d29b884dd77fe5e628dc71318de08868c Mon Sep 17 00:00:00 2001 From: Mateusz Stachyra <m.stachyra@samsung.com> Date: Mon, 3 Jul 2023 17:48:40 +0200 Subject: [PATCH] trace: fix null pointer dereference in tracing_err_log_open()
Fix an issue in function 'tracing_err_log_open'. The function doesn't call 'seq_open' if file is opened only with write permissions, which results in 'file->private_data' being left at null. If we then use 'lseek' on that opened file, 'seq_lseek' dereferences 'file->private_data' in 'mutex_lock(&m->lock)', resulting in a Kernel panic. Writing to this node requires root privilages, therefore this bug has very little security impact.
Tracefs node: /sys/kernel/tracing/error_log
Example Kernel panic:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000038 Call trace: mutex_lock+0x30/0x110 seq_lseek+0x34/0xb8 __arm64_sys_lseek+0x6c/0xb8 invoke_syscall+0x58/0x13c el0_svc_common+0xc4/0x10c do_el0_svc+0x24/0x98 el0_svc+0x24/0x88 el0t_64_sync_handler+0x84/0xe4 el0t_64_sync+0x1b4/0x1b8 Code: d503201f aa0803e0 aa1f03e1 aa0103e9 (c8e97d02) ---[ end trace 561d1b49c12cf8a5 ]--- Kernel panic - not syncing: Oops: Fatal exception
Signed-off-by: Mateusz Stachyra <m.stachyra@samsung.com> --- kernel/trace/trace.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 5d2c5678b..bfa8e2d01 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -8097,8 +8097,16 @@ static int tracing_err_log_open(struct inode *inode, struct file *file) return ret; /* If this file was opened for write, then erase contents */ - if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) + if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) { clear_tracing_err_log(tr); + ret = seq_open(file, &tracing_err_log_seq_ops); + if (!ret) { + struct seq_file *m = file->private_data; + m->private = tr; + } else { + trace_array_put(tr); + } + } if (file->f_mode & FMODE_READ) { ret = seq_open(file, &tracing_err_log_seq_ops); base-commit: 1ef6663a587ba3e57dc5065a477db1c64481eedd -- 2.25.1
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