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[fips-9] vsock fixes for CVE-2025-21756 - #243

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bmastbergen merged 2 commits into
fips-9-compliant/5.14.0-284.30.1from
bmastbergen_fips-9-compliant/5.14.0-284.30.1/VULN-53610
May 6, 2025
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[fips-9] vsock fixes for CVE-2025-21756#243
bmastbergen merged 2 commits into
fips-9-compliant/5.14.0-284.30.1from
bmastbergen_fips-9-compliant/5.14.0-284.30.1/VULN-53610

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@bmastbergenbmastbergen commented May 5, 2025

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VULN-53610
CVE-2025-21756

This ended up being two commits: The initial fix and a fix for that fix.

Build Log

/home/brett/kernel-src-tree
no .config file found, moving on
[TIMER]{MRPROPER}: 0s
x86_64 architecture detected, copying config
'configs/kernel-x86_64-rhel.config' -> '.config'
Setting Local Version for build
CONFIG_LOCALVERSION="-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e"
Making olddefconfig
HOSTCC scripts/basic/fixdep
HOSTCC scripts/kconfig/conf.o
HOSTCC scripts/kconfig/confdata.o
HOSTCC scripts/kconfig/expr.o
LEX scripts/kconfig/lexer.lex.c
YACC scripts/kconfig/parser.tab.[ch]
HOSTCC scripts/kconfig/lexer.lex.o
HOSTCC scripts/kconfig/menu.o
HOSTCC scripts/kconfig/parser.tab.o
HOSTCC scripts/kconfig/preprocess.o
HOSTCC scripts/kconfig/symbol.o
HOSTCC scripts/kconfig/util.o
HOSTLD scripts/kconfig/conf
#
# configuration written to .config
#
Starting Build
SYSHDR arch/x86/include/generated/uapi/asm/unistd_32.h
SYSHDR arch/x86/include/generated/uapi/asm/unistd_64.h
SYSHDR arch/x86/include/generated/uapi/asm/unistd_x32.h
SYSTBL arch/x86/include/generated/asm/syscalls_32.h
SYSHDR arch/x86/include/generated/asm/unistd_32_ia32.h
SYSHDR arch/x86/include/generated/asm/unistd_64_x32.h
SYSTBL arch/x86/include/generated/asm/syscalls_64.h
[SNIP]
INSTALL /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/xen/snd_xen_front.ko
INSTALL /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/virt/lib/irqbypass.ko
STRIP /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/usb/usx2y/snd-usb-us122l.ko
SIGN /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/usb/misc/snd-ua101.ko
STRIP /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/virtio/virtio_snd.ko
SIGN /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/usb/snd-usb-audio.ko
STRIP /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/usb/usx2y/snd-usb-usx2y.ko
SIGN /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/usb/snd-usbmidi-lib.ko
STRIP /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/virt/lib/irqbypass.ko
STRIP /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/xen/snd_xen_front.ko
STRIP /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/x86/snd-hdmi-lpe-audio.ko
SIGN /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/virtio/virtio_snd.ko
SIGN /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/usb/usx2y/snd-usb-us122l.ko
SIGN /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/virt/lib/irqbypass.ko
SIGN /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/usb/usx2y/snd-usb-usx2y.ko
SIGN /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/xen/snd_xen_front.ko
SIGN /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+/kernel/sound/x86/snd-hdmi-lpe-audio.ko
DEPMOD /lib/modules/5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+
[TIMER]{MODULES}: 10s
Making Install
sh ./arch/x86/boot/install.sh \
5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+ arch/x86/boot/bzImage \
System.map "/boot"
[TIMER]{INSTALL}: 45s
Checking kABI
Checking kABI
kABI check passed
Setting Default Kernel to /boot/vmlinuz-5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+ and Index to 2
Hopefully Grub2.0 took everything ... rebooting after time metrices
[TIMER]{MRPROPER}: 0s
[TIMER]{BUILD}: 1506s
[TIMER]{MODULES}: 10s
[TIMER]{INSTALL}: 45s
[TIMER]{TOTAL} 1577s
Rebooting in 10 seconds

Testing

kselftests were run before and after applying the changes

selftests-5.14.0-284.30.1.el9_2.ciqfips.0.11.1.x86_64.log

selftests-5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+.log

brett@lycia ~/ciq/vuln-53610 % grep ^ok selftests-5.14.0-284.30.1.el9_2.ciqfips.0.11.1.x86_64.log | wc -l
309
brett@lycia ~/ciq/vuln-53610 % grep ^ok selftests-5.14.0-b_f-9-c_5.14.0-284.30.1_VULN-53610-e910f8fffb5e+.log | wc -l
309
brett@lycia ~/ciq/vuln-53610 %

jira VULN-53610
cve CVE-2025-21756
commit-author Michal Luczaj <mhal@rbox.co>
commit fcdd224
upstream-diff Indentation is different from upstream change because
this kernel lacks 135ffc7 ("bpf, vsock: Invoke
proto::close on close()"). Otherwise the change
content is the same.
Preserve sockets bindings; this includes both resulting from an explicit
bind() and those implicitly bound through autobind during connect().
Prevents socket unbinding during a transport reassignment, which fixes a
use-after-free:
1. vsock_create() (refcnt=1) calls vsock_insert_unbound() (refcnt=2)
2. transport->release() calls vsock_remove_bound() without checking if
sk was bound and moved to bound list (refcnt=1)
3. vsock_bind() assumes sk is in unbound list and before
__vsock_insert_bound(vsock_bound_sockets()) calls
__vsock_remove_bound() which does:
list_del_init(&vsk->bound_table); // nop
sock_put(&vsk->sk); // refcnt=0
BUG: KASAN: slab-use-after-free in __vsock_bind+0x62e/0x730
Read of size 4 at addr ffff88816b46a74c by task a.out/2057
dump_stack_lvl+0x68/0x90
print_report+0x174/0x4f6
kasan_report+0xb9/0x190
__vsock_bind+0x62e/0x730
vsock_bind+0x97/0xe0
__sys_bind+0x154/0x1f0
__x64_sys_bind+0x6e/0xb0
do_syscall_64+0x93/0x1b0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Allocated by task 2057:
kasan_save_stack+0x1e/0x40
kasan_save_track+0x10/0x30
__kasan_slab_alloc+0x85/0x90
kmem_cache_alloc_noprof+0x131/0x450
sk_prot_alloc+0x5b/0x220
sk_alloc+0x2c/0x870
__vsock_create.constprop.0+0x2e/0xb60
vsock_create+0xe4/0x420
__sock_create+0x241/0x650
__sys_socket+0xf2/0x1a0
__x64_sys_socket+0x6e/0xb0
do_syscall_64+0x93/0x1b0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Freed by task 2057:
kasan_save_stack+0x1e/0x40
kasan_save_track+0x10/0x30
kasan_save_free_info+0x37/0x60
__kasan_slab_free+0x4b/0x70
kmem_cache_free+0x1a1/0x590
__sk_destruct+0x388/0x5a0
__vsock_bind+0x5e1/0x730
vsock_bind+0x97/0xe0
__sys_bind+0x154/0x1f0
__x64_sys_bind+0x6e/0xb0
do_syscall_64+0x93/0x1b0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 7 PID: 2057 at lib/refcount.c:25 refcount_warn_saturate+0xce/0x150
RIP: 0010:refcount_warn_saturate+0xce/0x150
__vsock_bind+0x66d/0x730
vsock_bind+0x97/0xe0
__sys_bind+0x154/0x1f0
__x64_sys_bind+0x6e/0xb0
do_syscall_64+0x93/0x1b0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
refcount_t: underflow; use-after-free.
WARNING: CPU: 7 PID: 2057 at lib/refcount.c:28 refcount_warn_saturate+0xee/0x150
RIP: 0010:refcount_warn_saturate+0xee/0x150
vsock_remove_bound+0x187/0x1e0
__vsock_release+0x383/0x4a0
vsock_release+0x90/0x120
__sock_release+0xa3/0x250
sock_close+0x14/0x20
__fput+0x359/0xa80
task_work_run+0x107/0x1d0
do_exit+0x847/0x2560
do_group_exit+0xb8/0x250
__x64_sys_exit_group+0x3a/0x50
x64_sys_call+0xfec/0x14f0
do_syscall_64+0x93/0x1b0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Fixes: c0cfa2d ("vsock: add multi-transports support")
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Link: https://patch.msgid.link/20250128-vsock-transport-vs-autobind-v3-1-1cf57065b770@rbox.co
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
(cherry picked from commit fcdd224)
Signed-off-by: Brett Mastbergen <bmastbergen@ciq.com>
jira VULN-53610
cve CVE-2025-21756
commit-author Michal Luczaj <mhal@rbox.co>
commit 78dafe1
upstream-diff Indentation is different from upstream change because
this kernel lacks 135ffc7 ("bpf, vsock: Invoke
proto::close on close()"). Otherwise the change
content is the same.
During socket release, sock_orphan() is called without considering that it
sets sk->sk_wq to NULL. Later, if SO_LINGER is enabled, this leads to a
null pointer dereferenced in virtio_transport_wait_close().
Orphan the socket only after transport release.
Partially reverts the 'Fixes:' commit.
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
lock_acquire+0x19e/0x500
_raw_spin_lock_irqsave+0x47/0x70
add_wait_queue+0x46/0x230
virtio_transport_release+0x4e7/0x7f0
__vsock_release+0xfd/0x490
vsock_release+0x90/0x120
__sock_release+0xa3/0x250
sock_close+0x14/0x20
__fput+0x35e/0xa90
__x64_sys_close+0x78/0xd0
do_syscall_64+0x93/0x1b0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Reported-by: syzbot+9d55b199192a4be7d02c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=9d55b199192a4be7d02c
Fixes: fcdd224 ("vsock: Keep the binding until socket destruction")
Tested-by: Luigi Leonardi <leonardi@redhat.com>
Reviewed-by: Luigi Leonardi <leonardi@redhat.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Link: https://patch.msgid.link/20250210-vsock-linger-nullderef-v3-1-ef6244d02b54@rbox.co
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
(cherry picked from commit 78dafe1)
Signed-off-by: Brett Mastbergen <bmastbergen@ciq.com>

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Thanks for the explanation in the upstream diff

:shipit:

@bmastbergen
bmastbergen merged commit 7de6dbc into fips-9-compliant/5.14.0-284.30.1May 6, 2025
@bmastbergen
bmastbergen deleted the bmastbergen_fips-9-compliant/5.14.0-284.30.1/VULN-53610 branch May 6, 2025 19:52
bmastbergen pushed a commit to bmastbergen/kernel-src-tree that referenced this pull request Aug 29, 2025
jira LE-1907
Rebuild_History Non-Buildable kernel-5.14.0-427.18.1.el9_4
commit-author Daniel Borkmann <daniel@iogearbox.net>
commit cd13c91
Add a big batch of test coverage to assert all aspects of the tcx opts
attach, detach and query API:
# ./vmtest.sh -- ./test_progs -t tc_opts
[...]
ctrliq#238 tc_opts_after:OK
ctrliq#239 tc_opts_append:OK
ctrliq#240 tc_opts_basic:OK
ctrliq#241 tc_opts_before:OK
ctrliq#242 tc_opts_chain_classic:OK
ctrliq#243 tc_opts_demixed:OK
ctrliq#244 tc_opts_detach:OK
ctrliq#245 tc_opts_detach_after:OK
ctrliq#246 tc_opts_detach_before:OK
ctrliq#247 tc_opts_dev_cleanup:OK
ctrliq#248 tc_opts_invalid:OK
ctrliq#249 tc_opts_mixed:OK
ctrliq#250 tc_opts_prepend:OK
ctrliq#251 tc_opts_replace:OK
ctrliq#252 tc_opts_revision:OK
Summary: 15/0 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20230719140858.13224-8-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit cd13c91)
Signed-off-by: Jonathan Maple <jmaple@ciq.com>
bmastbergen pushed a commit to bmastbergen/kernel-src-tree that referenced this pull request Aug 29, 2025
jira LE-1907
Rebuild_History Non-Buildable kernel-5.14.0-427.18.1.el9_4
commit-author Daniel Borkmann <daniel@iogearbox.net>
commit ccd9a8b
Add several new tcx test cases to improve test coverage. This also includes
a few new tests with ingress instead of clsact qdisc, to cover the fix from
commit dc644b5 ("tcx: Fix splat in ingress_destroy upon tcx_entry_free").
# ./test_progs -t tc
[...]
ctrliq#234 tc_links_after:OK
ctrliq#235 tc_links_append:OK
ctrliq#236 tc_links_basic:OK
ctrliq#237 tc_links_before:OK
ctrliq#238 tc_links_chain_classic:OK
ctrliq#239 tc_links_chain_mixed:OK
ctrliq#240 tc_links_dev_cleanup:OK
ctrliq#241 tc_links_dev_mixed:OK
ctrliq#242 tc_links_ingress:OK
ctrliq#243 tc_links_invalid:OK
ctrliq#244 tc_links_prepend:OK
ctrliq#245 tc_links_replace:OK
ctrliq#246 tc_links_revision:OK
ctrliq#247 tc_opts_after:OK
ctrliq#248 tc_opts_append:OK
ctrliq#249 tc_opts_basic:OK
ctrliq#250 tc_opts_before:OK
ctrliq#251 tc_opts_chain_classic:OK
ctrliq#252 tc_opts_chain_mixed:OK
ctrliq#253 tc_opts_delete_empty:OK
ctrliq#254 tc_opts_demixed:OK
ctrliq#255 tc_opts_detach:OK
ctrliq#256 tc_opts_detach_after:OK
ctrliq#257 tc_opts_detach_before:OK
ctrliq#258 tc_opts_dev_cleanup:OK
ctrliq#259 tc_opts_invalid:OK
ctrliq#260 tc_opts_mixed:OK
ctrliq#261 tc_opts_prepend:OK
ctrliq#262 tc_opts_replace:OK
ctrliq#263 tc_opts_revision:OK
[...]
Summary: 44/38 PASSED, 0 SKIPPED, 0 FAILED
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/8699efc284b75ccdc51ddf7062fa2370330dc6c0.1692029283.git.daniel@iogearbox.net
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
(cherry picked from commit ccd9a8b)
Signed-off-by: Jonathan Maple <jmaple@ciq.com>
github-actionsBot pushed a commit that referenced this pull request Jun 1, 2026
With CONFIG_CALL_DEPTH_TRACKING enabled on an x86 retbleed-affected platform
(eg: Skylake), with retbleed=stuff, registering a dynamic ftrace trampoline
crashes on the first call into the traced function:
BUG: unable to handle page fault for address: ffff88817ae18880
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 4b53067 P4D 4b53067 PUD 0
Oops: Oops: 0002 [#1] SMP PTI
CPU: 3 UID: 0 PID: 187 Comm: usleep Not tainted 7.0.10 #243 PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.17.0-2-2 04/01/2014
Code: 24 78 00 00 00 00 48 89 ea 48 89 54 24 20 48 8b b4 24 b8 00 00 00 48 8b bc 24 b0 00 00 00 48 89 bc 24 80 00 00 00 48 83 ef 05 <65> 48 c1 3d 1f a8 b6 02 05 48 8b 15 f6 00 00 00 4c 89 3c 24 4c 89
Call Trace:
<TASK>
? find_held_lock
? exc_page_fault
? lock_release
? __x64_sys_clock_nanosleep
? lockdep_hardirqs_on_prepare
? trace_hardirqs_on
__x64_sys_clock_nanosleep
do_syscall_64
? exc_page_fault
? call_depth_return_thunk
entry_SYSCALL_64_after_hwframe
...
Kernel panic - not syncing: Fatal exception
This small reproducer allows to easily trigger the crash:
# echo 'p __x64_sys_clock_nanosleep' > /sys/kernel/tracing/kprobe_events
# echo 1 > /sys/kernel/tracing/events/kprobes/p___x64_sys_clock_nanosleep_0/enable
# usleep 1
Monitoring the crash under GDB points to the exact instruction in charge of
incrementing the call depth:
sarq $5, %gs:__x86_call_depth(%rip)
This instruction matches the one inserted by the ftrace_regs_caller from
ftrace_64.S. This emitted code was likely working fine until the introduction
of
59bec00 ("x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR()"):
it has made the call depth accounting addressing relative to $rip, instead of
being based on an absolute address.
As this code exact location depends on where the trampoline lives in memory,
the corresponding displacement needs to be adjusted at runtime to actually
correctly find the per-cpu __x86_call_depth value, otherwise the targeted
address is wrong, leading to the page fault seen above.
Fix the %rip-relative displacement of the copied CALL_DEPTH_ACCOUNT
instruction (from ftrace_regs_caller) by calling text_poke_apply_relocation(),
as it is done for example by the x86 BPF JIT compiler through
x86_call_depth_emit_accounting(). This corrects both CALL_DEPTH_ACCOUNT slots,
in ftrace_caller and ftrace_regs_caller.
[ bp: Massage. ]
Fixes: 59bec00 ("x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR()")
Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260527-fix_call_depth_in_trampoline-v1-1-1c1abc8ae310@bootlin.com
github-actionsBot pushed a commit to athimm/kernel-src-tree that referenced this pull request Jun 9, 2026
[ Upstream commit a17dc12 ]
With CONFIG_CALL_DEPTH_TRACKING enabled on an x86 retbleed-affected platform
(eg: Skylake), with retbleed=stuff, registering a dynamic ftrace trampoline
crashes on the first call into the traced function:
BUG: unable to handle page fault for address: ffff88817ae18880
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 4b53067 P4D 4b53067 PUD 0
Oops: Oops: 0002 [ctrliq#1] SMP PTI
CPU: 3 UID: 0 PID: 187 Comm: usleep Not tainted 7.0.10 ctrliq#243 PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.17.0-2-2 04/01/2014
Code: 24 78 00 00 00 00 48 89 ea 48 89 54 24 20 48 8b b4 24 b8 00 00 00 48 8b bc 24 b0 00 00 00 48 89 bc 24 80 00 00 00 48 83 ef 05 <65> 48 c1 3d 1f a8 b6 02 05 48 8b 15 f6 00 00 00 4c 89 3c 24 4c 89
Call Trace:
<TASK>
? find_held_lock
? exc_page_fault
? lock_release
? __x64_sys_clock_nanosleep
? lockdep_hardirqs_on_prepare
? trace_hardirqs_on
__x64_sys_clock_nanosleep
do_syscall_64
? exc_page_fault
? call_depth_return_thunk
entry_SYSCALL_64_after_hwframe
...
Kernel panic - not syncing: Fatal exception
This small reproducer allows to easily trigger the crash:
# echo 'p __x64_sys_clock_nanosleep' > /sys/kernel/tracing/kprobe_events
# echo 1 > /sys/kernel/tracing/events/kprobes/p___x64_sys_clock_nanosleep_0/enable
# usleep 1
Monitoring the crash under GDB points to the exact instruction in charge of
incrementing the call depth:
sarq $5, %gs:__x86_call_depth(%rip)
This instruction matches the one inserted by the ftrace_regs_caller from
ftrace_64.S. This emitted code was likely working fine until the introduction
of
59bec00 ("x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR()"):
it has made the call depth accounting addressing relative to $rip, instead of
being based on an absolute address.
As this code exact location depends on where the trampoline lives in memory,
the corresponding displacement needs to be adjusted at runtime to actually
correctly find the per-cpu __x86_call_depth value, otherwise the targeted
address is wrong, leading to the page fault seen above.
Fix the %rip-relative displacement of the copied CALL_DEPTH_ACCOUNT
instruction (from ftrace_regs_caller) by calling text_poke_apply_relocation(),
as it is done for example by the x86 BPF JIT compiler through
x86_call_depth_emit_accounting(). This corrects both CALL_DEPTH_ACCOUNT slots,
in ftrace_caller and ftrace_regs_caller.
[ bp: Massage. ]
Fixes: 59bec00 ("x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR()")
Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260527-fix_call_depth_in_trampoline-v1-1-1c1abc8ae310@bootlin.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
github-actionsBot pushed a commit that referenced this pull request Jun 9, 2026
commit a17dc12 upstream.
With CONFIG_CALL_DEPTH_TRACKING enabled on an x86 retbleed-affected platform
(eg: Skylake), with retbleed=stuff, registering a dynamic ftrace trampoline
crashes on the first call into the traced function:
BUG: unable to handle page fault for address: ffff88817ae18880
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 4b53067 P4D 4b53067 PUD 0
Oops: Oops: 0002 [#1] SMP PTI
CPU: 3 UID: 0 PID: 187 Comm: usleep Not tainted 7.0.10 #243 PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.17.0-2-2 04/01/2014
Code: 24 78 00 00 00 00 48 89 ea 48 89 54 24 20 48 8b b4 24 b8 00 00 00 48 8b bc 24 b0 00 00 00 48 89 bc 24 80 00 00 00 48 83 ef 05 <65> 48 c1 3d 1f a8 b6 02 05 48 8b 15 f6 00 00 00 4c 89 3c 24 4c 89
Call Trace:
<TASK>
? find_held_lock
? exc_page_fault
? lock_release
? __x64_sys_clock_nanosleep
? lockdep_hardirqs_on_prepare
? trace_hardirqs_on
__x64_sys_clock_nanosleep
do_syscall_64
? exc_page_fault
? call_depth_return_thunk
entry_SYSCALL_64_after_hwframe
...
Kernel panic - not syncing: Fatal exception
This small reproducer allows to easily trigger the crash:
# echo 'p __x64_sys_clock_nanosleep' > /sys/kernel/tracing/kprobe_events
# echo 1 > /sys/kernel/tracing/events/kprobes/p___x64_sys_clock_nanosleep_0/enable
# usleep 1
Monitoring the crash under GDB points to the exact instruction in charge of
incrementing the call depth:
sarq $5, %gs:__x86_call_depth(%rip)
This instruction matches the one inserted by the ftrace_regs_caller from
ftrace_64.S. This emitted code was likely working fine until the introduction
of
59bec00 ("x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR()"):
it has made the call depth accounting addressing relative to $rip, instead of
being based on an absolute address.
As this code exact location depends on where the trampoline lives in memory,
the corresponding displacement needs to be adjusted at runtime to actually
correctly find the per-cpu __x86_call_depth value, otherwise the targeted
address is wrong, leading to the page fault seen above.
Fix the %rip-relative displacement of the copied CALL_DEPTH_ACCOUNT
instruction (from ftrace_regs_caller) by calling text_poke_apply_relocation(),
as it is done for example by the x86 BPF JIT compiler through
x86_call_depth_emit_accounting(). This corrects both CALL_DEPTH_ACCOUNT slots,
in ftrace_caller and ftrace_regs_caller.
[ bp: Massage. ]
Fixes: 59bec00 ("x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR()")
Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260527-fix_call_depth_in_trampoline-v1-1-1c1abc8ae310@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@bmastbergen@kerneltoast@PlaidCat