linux.git/kernel/trace/ftrace.c, branch v5.10.258

ftrace: Also allocate and copy hash for reading of filter files

2025-08-28T14:22:52+00:00

commit bfb336cf97df7b37b2b2edec0f69773e06d11955 upstream.

Currently the reader of set_ftrace_filter and set_ftrace_notrace just adds
the pointer to the global tracer hash to its iterator. Unlike the writer
that allocates a copy of the hash, the reader keeps the pointer to the
filter hashes. This is problematic because this pointer is static across
function calls that release the locks that can update the global tracer
hashes. This can cause UAF and similar bugs.

Allocate and copy the hash for reading the filter files like it is done
for the writers. This not only fixes UAF bugs, but also makes the code a
bit simpler as it doesn't have to differentiate when to free the
iterator's hash between writers and readers.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Cc: Nathan Chancellor 
Cc: Linus Torvalds 
Link: https://lore.kernel.org/20250822183606.12962cc3@batman.local.home
Fixes: c20489dad156 ("ftrace: Assign iter->hash to filter or notrace hashes on seq read")
Closes: https://lore.kernel.org/all/20250813023044.2121943-1-wutengda@huaweicloud.com/
Closes: https://lore.kernel.org/all/20250822192437.GA458494@ax162/
Reported-by: Tengda Wu 
Tested-by: Tengda Wu 
Tested-by: Nathan Chancellor 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

ftrace: Fix UAF when lookup kallsym after ftrace disabled

2025-06-27T10:04:14+00:00

commit f914b52c379c12288b7623bb814d0508dbe7481d upstream.

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:
 
 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.

Link: https://lore.kernel.org/all/20250523135452.626d8dcd@gandalf.local.home/

Cc: stable@vger.kernel.org
Fixes: aba4b5c22cba ("ftrace: Save module init functions kallsyms symbols for tracing")
Link: https://lore.kernel.org/20250529111955.2349189-2-yebin@huaweicloud.com
Signed-off-by: Ye Bin 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

ftrace: Add cond_resched() to ftrace_graph_set_hash()

2025-05-02T05:40:56+00:00

commit 42ea22e754ba4f2b86f8760ca27f6f71da2d982c upstream.

When the kernel contains a large number of functions that can be traced,
the loop in ftrace_graph_set_hash() may take a lot of time to execute.
This may trigger the softlockup watchdog.

Add cond_resched() within the loop to allow the kernel to remain
responsive even when processing a large number of functions.

This matches the cond_resched() that is used in other locations of the
code that iterates over all functions that can be traced.

Cc: stable@vger.kernel.org
Fixes: b9b0c831bed26 ("ftrace: Convert graph filter to use hash tables")
Link: https://lore.kernel.org/tencent_3E06CE338692017B5809534B9C5C03DA7705@qq.com
Signed-off-by: zhoumin 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

ftrace: Avoid potential division by zero in function_stat_show()

2025-03-13T11:47:33+00:00

commit a1a7eb89ca0b89dc1c326eeee2596f263291aca3 upstream.

Check whether denominator expression x * (x - 1) * 1000 mod {2^32, 2^64}
produce zero and skip stddev computation in that case.

For now don't care about rec->counter * rec->counter overflow because
rec->time * rec->time overflow will likely happen earlier.

Cc: stable@vger.kernel.org
Cc: Wen Yang 
Cc: Mark Rutland 
Cc: Mathieu Desnoyers 
Link: https://lore.kernel.org/20250206090156.1561783-1-kniv@yandex-team.ru
Fixes: e31f7939c1c27 ("ftrace: Avoid potential division by zero in function profiler")
Signed-off-by: Nikolay Kuratov 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

ftrace: Fix regression with module command in stack_trace_filter

2024-12-14T18:47:37+00:00

commit 45af52e7d3b8560f21d139b3759735eead8b1653 upstream.

When executing the following command:

    # echo "write*:mod:ext3" > /sys/kernel/tracing/stack_trace_filter

The current mod command causes a null pointer dereference. While commit
0f17976568b3f ("ftrace: Fix regression with module command in stack_trace_filter")
has addressed part of the issue, it left a corner case unhandled, which still
results in a kernel crash.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu 
Cc: Mark Rutland 
Cc: Mathieu Desnoyers 
Link: https://lore.kernel.org/20241120052750.275463-1-guoweikang.kernel@gmail.com
Fixes: 04ec7bb642b77 ("tracing: Have the trace_array hold the list of registered func probes");
Signed-off-by: guoweikang 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

ftrace: Fix possible use-after-free issue in ftrace_location()

2024-10-17T13:07:37+00:00

commit e60b613df8b6253def41215402f72986fee3fc8d upstream.

KASAN reports a bug:

  BUG: KASAN: use-after-free in ftrace_location+0x90/0x120
  Read of size 8 at addr ffff888141d40010 by task insmod/424
  CPU: 8 PID: 424 Comm: insmod Tainted: G        W          6.9.0-rc2+
  [...]
  Call Trace:
   
   dump_stack_lvl+0x68/0xa0
   print_report+0xcf/0x610
   kasan_report+0xb5/0xe0
   ftrace_location+0x90/0x120
   register_kprobe+0x14b/0xa40
   kprobe_init+0x2d/0xff0 [kprobe_example]
   do_one_initcall+0x8f/0x2d0
   do_init_module+0x13a/0x3c0
   load_module+0x3082/0x33d0
   init_module_from_file+0xd2/0x130
   __x64_sys_finit_module+0x306/0x440
   do_syscall_64+0x68/0x140
   entry_SYSCALL_64_after_hwframe+0x71/0x79

The root cause is that, in lookup_rec(), ftrace record of some address
is being searched in ftrace pages of some module, but those ftrace pages
at the same time is being freed in ftrace_release_mod() as the
corresponding module is being deleted:

           CPU1                       |      CPU2
  register_kprobes() {                | delete_module() {
    check_kprobe_address_safe() {     |
      arch_check_ftrace_location() {  |
        ftrace_location() {           |
          lookup_rec() // USE!        |   ftrace_release_mod() // Free!

To fix this issue:
  1. Hold rcu lock as accessing ftrace pages in ftrace_location_range();
  2. Use ftrace_location_range() instead of lookup_rec() in
     ftrace_location();
  3. Call synchronize_rcu() before freeing any ftrace pages both in
     ftrace_process_locs()/ftrace_release_mod()/ftrace_free_mem().

Link: https://lore.kernel.org/linux-trace-kernel/20240509192859.1273558-1-zhengyejian1@huawei.com

Cc: stable@vger.kernel.org
Cc: 
Cc: 
Cc: 
Fixes: ae6aa16fdc16 ("kprobes: introduce ftrace based optimization")
Suggested-by: Steven Rostedt 
Signed-off-by: Zheng Yejian 
Signed-off-by: Steven Rostedt (Google) 
[Shivani: Modified to apply on v5.10.y]
Signed-off-by: Shivani Agarwal 
Signed-off-by: Greg Kroah-Hartman

x86/ibt,ftrace: Search for fentry location

2024-10-17T13:07:37+00:00

commit aebfd12521d9c7d0b502cf6d06314cfbcdccfe3b upstream.

Currently a lot of ftrace code assumes __fentry__ is at sym+0. However
with Intel IBT enabled the first instruction of a function will most
likely be ENDBR.

Change ftrace_location() to not only return the __fentry__ location
when called for the __fentry__ location, but also when called for the
sym+0 location.

Then audit/update all callsites of this function to consistently use
these new semantics.

Suggested-by: Steven Rostedt 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Masami Hiramatsu 
Acked-by: Josh Poimboeuf 
Link: https://lore.kernel.org/r/20220308154318.227581603@infradead.org
Stable-dep-of: e60b613df8b6 ("ftrace: Fix possible use-after-free issue in ftrace_location()")
[Shivani: Modified to apply on v5.10.y]
Signed-off-by: Shivani Agarwal 
Signed-off-by: Greg Kroah-Hartman

ftrace: Fix possible warning on checking all pages used in ftrace_process_locs()

2023-07-27T06:44:44+00:00

commit 26efd79c4624294e553aeaa3439c646729bad084 upstream.

As comments in ftrace_process_locs(), there may be NULL pointers in
mcount_loc section:
 > Some architecture linkers will pad between
 > the different mcount_loc sections of different
 > object files to satisfy alignments.
 > Skip any NULL pointers.

After commit 20e5227e9f55 ("ftrace: allow NULL pointers in mcount_loc"),
NULL pointers will be accounted when allocating ftrace pages but skipped
before adding into ftrace pages, this may result in some pages not being
used. Then after commit 706c81f87f84 ("ftrace: Remove extra helper
functions"), warning may occur at:
  WARN_ON(pg->next);

To fix it, only warn for case that no pointers skipped but pages not used
up, then free those unused pages after releasing ftrace_lock.

Link: https://lore.kernel.org/linux-trace-kernel/20230712060452.3175675-1-zhengyejian1@huawei.com

Cc: stable@vger.kernel.org
Fixes: 706c81f87f84 ("ftrace: Remove extra helper functions")
Suggested-by: Steven Rostedt 
Signed-off-by: Zheng Yejian 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

ftrace: Store the order of pages allocated in ftrace_page

2023-07-27T06:44:43+00:00

commit db42523b4f3e83ff86b53cdda219a9767c8b047f upstream.

Instead of saving the size of the records field of the ftrace_page, store
the order it uses to allocate the pages, as that is what is needed to know
in order to free the pages. This simplifies the code.

Link: https://lore.kernel.org/lkml/CAHk-=whyMxheOqXAORt9a7JK9gc9eHTgCJ55Pgs4p=X3RrQubQ@mail.gmail.com/

Signed-off-by: Linus Torvalds 
[ change log written by Steven Rostedt ]
Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Zheng Yejian 
Signed-off-by: Greg Kroah-Hartman

ftrace: Fix issue that 'direct->addr' not restored in modify_ftrace_direct()

2023-04-20T10:10:23+00:00

commit 2a2d8c51defb446e8d89a83f42f8e5cd529111e9 upstream.

Syzkaller report a WARNING: "WARN_ON(!direct)" in modify_ftrace_direct().

Root cause is 'direct->addr' was changed from 'old_addr' to 'new_addr' but
not restored if error happened on calling ftrace_modify_direct_caller().
Then it can no longer find 'direct' by that 'old_addr'.

To fix it, restore 'direct->addr' to 'old_addr' explicitly in error path.

Link: https://lore.kernel.org/linux-trace-kernel/20230330025223.1046087-1-zhengyejian1@huawei.com

Cc: stable@vger.kernel.org
Cc: 
Cc: 
Cc: 
Cc: 
Fixes: 8a141dd7f706 ("ftrace: Fix modify_ftrace_direct.")
Signed-off-by: Zheng Yejian 
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman