6.14-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Richter tmricht@linux.ibm.com
[ Upstream commit aa1ac98268cd1f380c713f07e39b1fa1d5c7650c ]
In PMU event initialization functions - cpumsf_pmu_event_init() - cpumf_pmu_event_init() - cfdiag_event_init() the partially created event had to be removed when an error was detected. The event::event_init() member function had to release all resources it allocated in case of error. event::destroy() had to be called on freeing an event after it was successfully created and event::event_init() returned success.
With
commit c70ca298036c ("perf/core: Simplify the perf_event_alloc() error path")
this is not necessary anymore. The performance subsystem common code now always calls event::destroy() to clean up the allocated resources created during event initialization.
Remove the event::destroy() invocation in PMU event initialization or that function is called twice for each event that runs into an error condition in event creation.
This is the kernel log entry which shows up without the fix:
------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 43388 at lib/refcount.c:87 refcount_dec_not_one+0x74/0x90 CPU: 0 UID: 0 PID: 43388 Comm: perf Not tainted 6.15.0-20250407.rc1.git0.300.fc41.s390x+git #1 NONE Hardware name: IBM 3931 A01 704 (LPAR) Krnl PSW : 0704c00180000000 00000209cb2c1b88 (refcount_dec_not_one+0x78/0x90) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3 Krnl GPRS: 0000020900000027 0000020900000023 0000000000000026 0000018900000000 00000004a2200a00 0000000000000000 0000000000000057 ffffffffffffffea 00000002b386c600 00000002b3f5b3e0 00000209cc51f140 00000209cc7fc550 0000000001449d38 ffffffffffffffff 00000209cb2c1b84 00000189d67dfb80 Krnl Code: 00000209cb2c1b78: c02000506727 larl %r2,00000209cbcce9c6 00000209cb2c1b7e: c0e5ffbd4431 brasl %r14,00000209caa6a3e0 #00000209cb2c1b84: af000000 mc 0,0 >00000209cb2c1b88: a7480001 lhi %r4,1 00000209cb2c1b8c: ebeff0a00004 lmg %r14,%r15,160(%r15) 00000209cb2c1b92: ec243fbf0055 risbg %r2,%r4,63,191,0 00000209cb2c1b98: 07fe bcr 15,%r14 00000209cb2c1b9a: 47000700 bc 0,1792 Call Trace: [<00000209cb2c1b88>] refcount_dec_not_one+0x78/0x90 [<00000209cb2c1dc4>] refcount_dec_and_mutex_lock+0x24/0x90 [<00000209caa3c29e>] hw_perf_event_destroy+0x2e/0x80 [<00000209cacaf8b4>] __free_event+0x74/0x270 [<00000209cacb47c4>] perf_event_alloc.part.0+0x4a4/0x730 [<00000209cacbf3e8>] __do_sys_perf_event_open+0x248/0xc20 [<00000209cacc14a4>] __s390x_sys_perf_event_open+0x44/0x50 [<00000209cb8114de>] __do_syscall+0x12e/0x260 [<00000209cb81ce34>] system_call+0x74/0x98 Last Breaking-Event-Address: [<00000209caa6a4d2>] __warn_printk+0xf2/0x100 ---[ end trace 0000000000000000 ]---
Fixes: c70ca298036c ("perf/core: Simplify the perf_event_alloc() error path") Signed-off-by: Thomas Richter tmricht@linux.ibm.com Reviewed-by: Sumanth Korikkar sumanthk@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/kernel/perf_cpum_cf.c | 9 +-------- arch/s390/kernel/perf_cpum_sf.c | 3 --- 2 files changed, 1 insertion(+), 11 deletions(-)
diff --git a/arch/s390/kernel/perf_cpum_cf.c b/arch/s390/kernel/perf_cpum_cf.c index 33205dd410e47..60a60185b1d4d 100644 --- a/arch/s390/kernel/perf_cpum_cf.c +++ b/arch/s390/kernel/perf_cpum_cf.c @@ -858,18 +858,13 @@ static int cpumf_pmu_event_type(struct perf_event *event) static int cpumf_pmu_event_init(struct perf_event *event) { unsigned int type = event->attr.type; - int err; + int err = -ENOENT;
if (type == PERF_TYPE_HARDWARE || type == PERF_TYPE_RAW) err = __hw_perf_event_init(event, type); else if (event->pmu->type == type) /* Registered as unknown PMU */ err = __hw_perf_event_init(event, cpumf_pmu_event_type(event)); - else - return -ENOENT; - - if (unlikely(err) && event->destroy) - event->destroy(event);
return err; } @@ -1819,8 +1814,6 @@ static int cfdiag_event_init(struct perf_event *event) event->destroy = hw_perf_event_destroy;
err = cfdiag_event_init2(event); - if (unlikely(err)) - event->destroy(event); out: return err; } diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c index 5f60248cb4687..ad22799d8a7d9 100644 --- a/arch/s390/kernel/perf_cpum_sf.c +++ b/arch/s390/kernel/perf_cpum_sf.c @@ -885,9 +885,6 @@ static int cpumsf_pmu_event_init(struct perf_event *event) event->attr.exclude_idle = 0;
err = __hw_perf_event_init(event); - if (unlikely(err)) - if (event->destroy) - event->destroy(event); return err; }