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Levin" , Guo Ren , Palmer Dabbelt , Emil Renner Berthing , Felix Yan , Ruizhe Pan , Celeste Liu , stable@vger.kernel.org Subject: [PATCH] riscv: entry: always initialize regs->a0 to -ENOSYS Date: Thu, 27 Jun 2024 18:32:06 +0800 Message-ID: <20240627103205.27914-2-CoelacanthusHex@gmail.com> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1216; i=CoelacanthusHex@gmail.com; h=from:subject; bh=uImnSU73FfppRnJFjnbhQ8DpGMuTK/5eh1Eqwdt64C0=; b=owJ4nJvAy8zAJfY4pvNJRPo6U8bTakkMabX2S2McK1/saakP2s0R0KXLcMA0af+nj7u0UhOjr c3nfI8T0esoZWEQ42KQFVNkEdv59PWy0kcflvGazICZw8oEMoSBi1MAJvJLn+F/FM/dIrs57xuX vOp8wT5NySJji5qvn+/SDz6ODkfZE/9pMPwvnf8q5NEJU36D1tPSzl2l5R9Wv5DXfpVgUXWx8LT Z9b0cAI4SS+4= X-Developer-Key: i=CoelacanthusHex@gmail.com; a=openpgp; fpr=892EBC7DC392DFF9C9C03F1D15F4180E73787863 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Otherwise when the tracer changes syscall number to -1, the kernel fails to initialize a0 with -ENOSYS and subsequently fails to return the error code of the failed syscall to userspace. For example, it will break strace syscall tampering. Fixes: 52449c17bdd1 ("riscv: entry: set a0 =3D -ENOSYS only when syscall != =3D -1") Cc: stable@vger.kernel.org Signed-off-by: Celeste Liu Reported-by: "Dmitry V. Levin" Reviewed-by: Bj=C3=B6rn T=C3=B6pel --- arch/riscv/kernel/traps.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index 05a16b1f0aee..51ebfd23e007 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -319,6 +319,7 @@ void do_trap_ecall_u(struct pt_regs *regs) =20 regs->epc +=3D 4; regs->orig_a0 =3D regs->a0; + regs->a0 =3D -ENOSYS; =20 riscv_v_vstate_discard(regs); =20 @@ -328,8 +329,7 @@ void do_trap_ecall_u(struct pt_regs *regs) =20 if (syscall >=3D 0 && syscall < NR_syscalls) syscall_handler(regs, syscall); - else if (syscall !=3D -1) - regs->a0 =3D -ENOSYS; + /* * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(), * so the maximum stack offset is 1k bytes (10 bits). --=20 2.45.2