Steven Rostedt (Google) 2fa74d29fc tracing: Have trace_event_file have ref counters ... commit bb32500fb9 upstream. The following can crash the kernel: # cd /sys/kernel/tracing # echo 'p:sched schedule' > kprobe_events # exec 5>>events/kprobes/sched/enable # > kprobe_events # exec 5>&- The above commands: 1. Change directory to the tracefs directory 2. Create a kprobe event (doesn't matter what one) 3. Open bash file descriptor 5 on the enable file of the kprobe event 4. Delete the kprobe event (removes the files too) 5. Close the bash file descriptor 5 The above causes a crash! BUG: kernel NULL pointer dereference, address: 0000000000000028 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 6 PID: 877 Comm: bash Not tainted 6.5.0-rc4-test-00008-g2c6b6b1029d4-dirty #186 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 RIP: 0010:tracing_release_file_tr+0xc/0x50 What happens here is that the kprobe event creates a trace_event_file "file" descriptor that represents the file in tracefs to the event. It maintains state of the event (is it enabled for the given instance?). Opening the "enable" file gets a reference to the event "file" descriptor via the open file descriptor. When the kprobe event is deleted, the file is also deleted from the tracefs system which also frees the event "file" descriptor. But as the tracefs file is still opened by user space, it will not be totally removed until the final dput() is called on it. But this is not true with the event "file" descriptor that is already freed. If the user does a write to or simply closes the file descriptor it will reference the event "file" descriptor that was just freed, causing a use-after-free bug. To solve this, add a ref count to the event "file" descriptor as well as a new flag called "FREED". The "file" will not be freed until the last reference is released. But the FREE flag will be set when the event is removed to prevent any more modifications to that event from happening, even if there's still a reference to the event "file" descriptor. Link: https://lore.kernel.org/linux-trace-kernel/20231031000031.1e705592@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20231031122453.7a48b923@gandalf.local.home Cc: stable@vger.kernel.org Cc: Mark Rutland <mark.rutland@arm.com> Fixes: f5ca233e2e ("tracing: Increase trace array ref count on enable and filter files") Reported-by: Beau Belgrave <beaub@linux.microsoft.com> Tested-by: Beau Belgrave <beaub@linux.microsoft.com> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2023-11-28 17:07:23 +00:00
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acpi	…
asm-generic	…
clocksource	…
crypto	…
drm	gpu/drm: Eliminate DRM_SCHED_PRIORITY_UNSET	2023-11-08 14:11:00 +01:00
dt-bindings	…
keys	…
kunit	kunit: add macro to allow conditionally exposing static symbols to tests	2023-11-20 11:52:08 +01:00
kvm	…
linux	tracing: Have trace_event_file have ref counters	2023-11-28 17:07:23 +00:00
math-emu	…
media	media: cec: core: add adap_unconfigured() callback	2023-09-13 09:42:54 +02:00
memory	…
misc	…
net	netfilter: nf_tables: fix pointer math issue in nft_byteorder_eval()	2023-11-28 17:07:05 +00:00
pcmcia	…
ras	…
rdma	…
rv	…
scsi	scsi: sd: Introduce manage_shutdown device flag	2023-11-02 09:35:29 +01:00
soc	…
sound	ASoC: SOF: Pass PCI SSID to machine driver	2023-11-28 17:06:58 +00:00
target	…
trace	neighbor: tracing: Move pin6 inside CONFIG_IPV6=y section	2023-10-25 12:03:07 +02:00
uapi	vsock: read from socket's error queue	2023-11-28 17:06:56 +00:00
ufs	…
vdso	…
video	…
xen	…