diff options
| author | Daniel Paziyski <danielpaziyski@gmail.com> | 2026-07-10 15:40:54 +0200 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2026-07-13 06:24:36 -0700 |
| commit | 9c66085e6dcfb44b70970aa4e323003fc7f2b738 (patch) | |
| tree | 85b90dc4538e3f6a9a1bc8e406f2404a6daf0f50 | |
| parent | cfbebb55e5127dc162e73fa8956000055a78606c (diff) | |
KVM: x86: Fix null pointer deref due to dummy array in trace_kvm_inj_exception()
The trace_kvm_inj_exception tracepoint takes as arguments the exception
vector, whether the exception has an error code (and subsequently, the
error code), and whether it is being reinjected. Because '0' is a valid
error code, KVM uses __print_symbolic() to format the error code as a
string to avoid printing the error code entirely if the exception doesn't
have an error code (see commit 21d4c575eb4a ("KVM: x86: Print error code
in exception injection tracepoint iff valid").
KVM's abuse of __print_symbolic() was all fine and dandy, until commit
754e38d2d1ae ("tracing: Use explicit array size instead of sentinel
elements in symbol printing") reworked the printing to avoid terminating
the arrays with NULL/0 values, and missed KVM's clever use of not-quite
empty array of symbols.
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: Oops: 0000 [#1] SMP
CPU: 20 UID: 0 PID: 791 Comm: less Not tainted 7.2.0-rc2 #401 PREEMPT
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:strlen+0x0/0x20
Call Trace:
<TASK>
trace_seq_puts+0x18/0x80
trace_print_symbols_seq+0x68/0xa0
trace_raw_output_kvm_inj_exception+0x64/0xf0 [kvm]
s_show+0x47/0x110
seq_read_iter+0x2a5/0x4c0
seq_read+0xfd/0x130
vfs_read+0xb6/0x330
? vfs_write+0x2f2/0x3f0
ksys_read+0x61/0xd0
do_syscall_64+0xb7/0x570
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x7ff283714862
</TASK>
Simply drop the dummy array entirely, so that __print_symbolic() generates
a truly empty array.
Signed-off-by: Daniel Paziyski <danielpaziyski@gmail.com>
Fixes: 754e38d2d1ae ("tracing: Use explicit array size instead of sentinel elements in symbol printing")
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://patch.msgid.link/20260710134055.16432-1-danielpaziyski@gmail.com
[sean: massage changelog, add splat, add Fixes, cc stable]
Signed-off-by: Sean Christopherson <seanjc@google.com>
| -rw-r--r-- | arch/x86/kvm/trace.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h index 0db25bba17f6..93de876c318c 100644 --- a/arch/x86/kvm/trace.h +++ b/arch/x86/kvm/trace.h @@ -490,7 +490,7 @@ TRACE_EVENT(kvm_inj_exception, TP_printk("%s%s%s%s%s", __print_symbolic(__entry->exception, kvm_trace_sym_exc), !__entry->has_error ? "" : " (", - !__entry->has_error ? "" : __print_symbolic(__entry->error_code, { }), + !__entry->has_error ? "" : __print_symbolic(__entry->error_code), !__entry->has_error ? "" : ")", __entry->reinjected ? " [reinjected]" : "") ); |