CVE-2025-38346

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

ftrace: Fix UAF when lookup kallsym after ftrace disabled

The following issue happens with a buggy module:

BUG: unable to handle page fault for address: ffffffffc05d0218

PGD 1bd66f067 P4D 1bd66f067 PUD 1bd671067 PMD 101808067 PTE 0

Oops: Oops: 0000 [#1] SMP KASAN PTI

Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS

RIP: 0010:sized_strscpy+0x81/0x2f0

RSP: 0018:ffff88812d76fa08 EFLAGS: 00010246

RAX: 0000000000000000 RBX: ffffffffc0601010 RCX: dffffc0000000000

RDX: 0000000000000038 RSI: dffffc0000000000 RDI: ffff88812608da2d

RBP: 8080808080808080 R08: ffff88812608da2d R09: ffff88812608da68

R10: ffff88812608d82d R11: ffff88812608d810 R12: 0000000000000038

R13: ffff88812608da2d R14: ffffffffc05d0218 R15: fefefefefefefeff

FS: 00007fef552de740(0000) GS:ffff8884251c7000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: ffffffffc05d0218 CR3: 00000001146f0000 CR4: 00000000000006f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Call Trace:

<TASK>

ftrace_mod_get_kallsym+0x1ac/0x590

update_iter_mod+0x239/0x5b0

s_next+0x5b/0xa0

seq_read_iter+0x8c9/0x1070

seq_read+0x249/0x3b0

proc_reg_read+0x1b0/0x280

vfs_read+0x17f/0x920

ksys_read+0xf3/0x1c0

do_syscall_64+0x5f/0x2e0

entry_SYSCALL_64_after_hwframe+0x76/0x7e

The above issue may happen as follows:

(1) Add kprobe tracepoint;

(2) insmod test.ko;

(3) Module triggers ftrace disabled;

(4) rmmod test.ko;

(5) cat /proc/kallsyms; --> Will trigger UAF as test.ko already removed;

ftrace_mod_get_kallsym()

...

strscpy(module_name, mod_map->mod->name, MODULE_NAME_LEN);

...

The problem is when a module triggers an issue with ftrace and

sets ftrace_disable. The ftrace_disable is set when an anomaly is

discovered and to prevent any more damage, ftrace stops all text

modification. The issue that happened was that the ftrace_disable stops

more than just the text modification.

When a module is loaded, its init functions can also be traced. Because

kallsyms deletes the init functions after a module has loaded, ftrace

saves them when the module is loaded and function tracing is enabled. This

allows the output of the function trace to show the init function names

instead of just their raw memory addresses.

When a module is removed, ftrace_release_mod() is called, and if

ftrace_disable is set, it just returns without doing anything more. The

problem here is that it leaves the mod_list still around and if kallsyms

is called, it will call into this code and access the module memory that

has already been freed as it will return:

strscpy(module_name, mod_map->mod->name, MODULE_NAME_LEN);

Where the "mod" no longer exists and triggers a UAF bug.