CVE-2022-49802

In the Linux kernel, the following vulnerability has been resolved:

ftrace: Fix null pointer dereference in ftrace_add_mod()

The @ftrace_mod is allocated by kzalloc(), so both the members {prev,next} of @ftrace_mode->list are NULL, it's not a valid state to call list_del(). If kstrdup() for @ftrace_mod->{func|module} fails, it goes to @out_free tag and calls free_ftrace_mod() to destroy @ftrace_mod, then list_del() will write prev->next and next->prev, where null pointer dereference happens.

BUG: kernel NULL pointer dereference, address: 0000000000000008 Oops: 0002 [#1] PREEMPT SMP NOPTI Call Trace: <TASK> ftrace_mod_callback+0x20d/0x220 ? do_filp_open+0xd9/0x140 ftrace_process_regex.isra.51+0xbf/0x130 ftrace_regex_write.isra.52.part.53+0x6e/0x90 vfs_write+0xee/0x3a0 ? __audit_filter_op+0xb1/0x100 ? auditd_test_task+0x38/0x50 ksys_write+0xa5/0xe0 do_syscall_64+0x3a/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd Kernel panic - not syncing: Fatal exception

So call INIT_LIST_HEAD() to initialize the list member to fix this issue.

The patch fixes a kernel NULL pointer dereference in the ftrace_add_mod() function. When memory allocation (kzalloc()) succeeds but subsequent kstrdup() fails, the error path calls list_del() on an uninitialized list head (ftrace_mod->list). This leads to a kernel panic due to prev->next or next->prev being NULL. This bug can be triggered by local privileged users (typically those interacting with Ftrace via debugfs or similar kernel tracing interfaces).

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.