mm/kmemleak: fix sleeping function called from invalid context at print message

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

mm/kmemleak: fix sleeping function called from invalid context at print message

Address a bug in the kernel that triggers a "sleeping function called from

invalid context" warning when /sys/kernel/debug/kmemleak is printed under

specific conditions:

- CONFIG_PREEMPT_RT=y

- Set SELinux as the LSM for the system

- Set kptr_restrict to 1

- kmemleak buffer contains at least one item

BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48

in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 136, name: cat

preempt_count: 1, expected: 0

RCU nest depth: 2, expected: 2

6 locks held by cat/136:

#0: ffff32e64bcbf950 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xb8/0xe30

#1: ffffafe6aaa9dea0 (scan_mutex){+.+.}-{3:3}, at: kmemleak_seq_start+0x34/0x128

#3: ffff32e6546b1cd0 (&object->lock){....}-{2:2}, at: kmemleak_seq_show+0x3c/0x1e0

#4: ffffafe6aa8d8560 (rcu_read_lock){....}-{1:2}, at: has_ns_capability_noaudit+0x8/0x1b0

#5: ffffafe6aabbc0f8 (notif_lock){+.+.}-{2:2}, at: avc_compute_av+0xc4/0x3d0

irq event stamp: 136660

hardirqs last enabled at (136659): [<ffffafe6a80fd7a0>] _raw_spin_unlock_irqrestore+0xa8/0xd8

hardirqs last disabled at (136660): [<ffffafe6a80fd85c>] _raw_spin_lock_irqsave+0x8c/0xb0

softirqs last enabled at (0): [<ffffafe6a5d50b28>] copy_process+0x11d8/0x3df8

softirqs last disabled at (0): [<0000000000000000>] 0x0

Preemption disabled at:

[<ffffafe6a6598a4c>] kmemleak_seq_show+0x3c/0x1e0

CPU: 1 UID: 0 PID: 136 Comm: cat Tainted: G E 6.11.0-rt7+ #34

Tainted: [E]=UNSIGNED_MODULE

Hardware name: linux,dummy-virt (DT)

Call trace:

dump_backtrace+0xa0/0x128

show_stack+0x1c/0x30

dump_stack_lvl+0xe8/0x198

dump_stack+0x18/0x20

rt_spin_lock+0x8c/0x1a8

avc_perm_nonode+0xa0/0x150

cred_has_capability.isra.0+0x118/0x218

selinux_capable+0x50/0x80

security_capable+0x7c/0xd0

has_ns_capability_noaudit+0x94/0x1b0

has_capability_noaudit+0x20/0x30

restricted_pointer+0x21c/0x4b0

pointer+0x298/0x760

vsnprintf+0x330/0xf70

seq_printf+0x178/0x218

print_unreferenced+0x1a4/0x2d0

kmemleak_seq_show+0xd0/0x1e0

seq_read_iter+0x354/0xe30

seq_read+0x250/0x378

full_proxy_read+0xd8/0x148

vfs_read+0x190/0x918

ksys_read+0xf0/0x1e0

__arm64_sys_read+0x70/0xa8

invoke_syscall.constprop.0+0xd4/0x1d8

el0_svc+0x50/0x158

el0t_64_sync+0x17c/0x180

%pS and %pK, in the same back trace line, are redundant, and %pS can void

%pK service in certain contexts.

%pS alone already provides the necessary information, and if it cannot

resolve the symbol, it falls back to printing the raw address voiding

the original intent behind the %pK.

Additionally, %pK requires a privilege check CAP_SYSLOG enforced through

the LSM, which can trigger a "sleeping function called from invalid

context" warning under RT_PREEMPT kernels when the check occurs in an

atomic context. This issue may also affect other LSMs.

This change avoids the unnecessary privilege check and resolves the

sleeping function warning without any loss of information.