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Linux Kernel: RISC-V 'sbi_ecall' Tracing Locks Up System
CVE-2026-23217
Summary
A bug in the Linux kernel can cause a specific type of tracing to lock up the system if certain conditions are met. This issue affects RISC-V systems, but it's easy to fix by disabling tracing of one specific kernel function. You can safely log sbi ecall events without tracing the function itself, so no functionality will be lost.
Original title
In the Linux kernel, the following vulnerability has been resolved:
riscv: trace: fix snapshot deadlock with sbi ecall
If sbi_ecall.c's functions are traceable,
echo "__sbi_ecall:snapshot" > /sy...
Original description
In the Linux kernel, the following vulnerability has been resolved:
riscv: trace: fix snapshot deadlock with sbi ecall
If sbi_ecall.c's functions are traceable,
echo "__sbi_ecall:snapshot" > /sys/kernel/tracing/set_ftrace_filter
may get the kernel into a deadlock.
(Functions in sbi_ecall.c are excluded from tracing if
CONFIG_RISCV_ALTERNATIVE_EARLY is set.)
__sbi_ecall triggers a snapshot of the ringbuffer. The snapshot code
raises an IPI interrupt, which results in another call to __sbi_ecall
and another snapshot...
All it takes to get into this endless loop is one initial __sbi_ecall.
On RISC-V systems without SSTC extension, the clock events in
timer-riscv.c issue periodic sbi ecalls, making the problem easy to
trigger.
Always exclude the sbi_ecall.c functions from tracing to fix the
potential deadlock.
sbi ecalls can easiliy be logged via trace events, excluding ecall
functions from function tracing is not a big limitation.
riscv: trace: fix snapshot deadlock with sbi ecall
If sbi_ecall.c's functions are traceable,
echo "__sbi_ecall:snapshot" > /sys/kernel/tracing/set_ftrace_filter
may get the kernel into a deadlock.
(Functions in sbi_ecall.c are excluded from tracing if
CONFIG_RISCV_ALTERNATIVE_EARLY is set.)
__sbi_ecall triggers a snapshot of the ringbuffer. The snapshot code
raises an IPI interrupt, which results in another call to __sbi_ecall
and another snapshot...
All it takes to get into this endless loop is one initial __sbi_ecall.
On RISC-V systems without SSTC extension, the clock events in
timer-riscv.c issue periodic sbi ecalls, making the problem easy to
trigger.
Always exclude the sbi_ecall.c functions from tracing to fix the
potential deadlock.
sbi ecalls can easiliy be logged via trace events, excluding ecall
functions from function tracing is not a big limitation.
Published: 18 Feb 2026 · Updated: 11 Mar 2026 · First seen: 6 Mar 2026