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    Subject[PATCH AUTOSEL 6.8 22/43] MIPS: scall: Save thread_info.syscall unconditionally on entry
    Date
    From: Jiaxun Yang <jiaxun.yang@flygoat.com>

    [ Upstream commit 4370b673ccf240bf7587b0cb8e6726a5ccaf1f17 ]

    thread_info.syscall is used by syscall_get_nr to supply syscall nr
    over a thread stack frame.

    Previously, thread_info.syscall is only saved at syscall_trace_enter
    when syscall tracing is enabled. However rest of the kernel code do
    expect syscall_get_nr to be available without syscall tracing. The
    previous design breaks collect_syscall.

    Move saving process to syscall entry to fix it.

    Reported-by: Xi Ruoyao <xry111@xry111.site>
    Link: https://github.com/util-linux/util-linux/issues/2867
    Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
    Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/mips/include/asm/ptrace.h | 2 +-
    arch/mips/kernel/asm-offsets.c | 1 +
    arch/mips/kernel/ptrace.c | 15 ++++++---------
    arch/mips/kernel/scall32-o32.S | 23 +++++++++++++----------
    arch/mips/kernel/scall64-n32.S | 3 ++-
    arch/mips/kernel/scall64-n64.S | 3 ++-
    arch/mips/kernel/scall64-o32.S | 33 +++++++++++++++++----------------
    7 files changed, 42 insertions(+), 38 deletions(-)

    diff --git a/arch/mips/include/asm/ptrace.h b/arch/mips/include/asm/ptrace.h
    index d14d0e37ad02d..4a2b40ce39e09 100644
    --- a/arch/mips/include/asm/ptrace.h
    +++ b/arch/mips/include/asm/ptrace.h
    @@ -159,7 +159,7 @@ extern unsigned long exception_ip(struct pt_regs *regs);
    #define exception_ip(regs) exception_ip(regs)
    #define profile_pc(regs) instruction_pointer(regs)

    -extern asmlinkage long syscall_trace_enter(struct pt_regs *regs, long syscall);
    +extern asmlinkage long syscall_trace_enter(struct pt_regs *regs);
    extern asmlinkage void syscall_trace_leave(struct pt_regs *regs);

    extern void die(const char *, struct pt_regs *) __noreturn;
    diff --git a/arch/mips/kernel/asm-offsets.c b/arch/mips/kernel/asm-offsets.c
    index d1b11f66f748f..cb1045ebab062 100644
    --- a/arch/mips/kernel/asm-offsets.c
    +++ b/arch/mips/kernel/asm-offsets.c
    @@ -101,6 +101,7 @@ void output_thread_info_defines(void)
    OFFSET(TI_CPU, thread_info, cpu);
    OFFSET(TI_PRE_COUNT, thread_info, preempt_count);
    OFFSET(TI_REGS, thread_info, regs);
    + OFFSET(TI_SYSCALL, thread_info, syscall);
    DEFINE(_THREAD_SIZE, THREAD_SIZE);
    DEFINE(_THREAD_MASK, THREAD_MASK);
    DEFINE(_IRQ_STACK_SIZE, IRQ_STACK_SIZE);
    diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c
    index 59288c13b581b..61503a36067e9 100644
    --- a/arch/mips/kernel/ptrace.c
    +++ b/arch/mips/kernel/ptrace.c
    @@ -1317,16 +1317,13 @@ long arch_ptrace(struct task_struct *child, long request,
    * Notification of system call entry/exit
    * - triggered by current->work.syscall_trace
    */
    -asmlinkage long syscall_trace_enter(struct pt_regs *regs, long syscall)
    +asmlinkage long syscall_trace_enter(struct pt_regs *regs)
    {
    user_exit();

    - current_thread_info()->syscall = syscall;
    -
    if (test_thread_flag(TIF_SYSCALL_TRACE)) {
    if (ptrace_report_syscall_entry(regs))
    return -1;
    - syscall = current_thread_info()->syscall;
    }

    #ifdef CONFIG_SECCOMP
    @@ -1335,7 +1332,7 @@ asmlinkage long syscall_trace_enter(struct pt_regs *regs, long syscall)
    struct seccomp_data sd;
    unsigned long args[6];

    - sd.nr = syscall;
    + sd.nr = current_thread_info()->syscall;
    sd.arch = syscall_get_arch(current);
    syscall_get_arguments(current, regs, args);
    for (i = 0; i < 6; i++)
    @@ -1345,23 +1342,23 @@ asmlinkage long syscall_trace_enter(struct pt_regs *regs, long syscall)
    ret = __secure_computing(&sd);
    if (ret == -1)
    return ret;
    - syscall = current_thread_info()->syscall;
    }
    #endif

    if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
    trace_sys_enter(regs, regs->regs[2]);

    - audit_syscall_entry(syscall, regs->regs[4], regs->regs[5],
    + audit_syscall_entry(current_thread_info()->syscall,
    + regs->regs[4], regs->regs[5],
    regs->regs[6], regs->regs[7]);

    /*
    * Negative syscall numbers are mistaken for rejected syscalls, but
    * won't have had the return value set appropriately, so we do so now.
    */
    - if (syscall < 0)
    + if (current_thread_info()->syscall < 0)
    syscall_set_return_value(current, regs, -ENOSYS, 0);
    - return syscall;
    + return current_thread_info()->syscall;
    }

    /*
    diff --git a/arch/mips/kernel/scall32-o32.S b/arch/mips/kernel/scall32-o32.S
    index 18dc9b3450561..2c604717e6308 100644
    --- a/arch/mips/kernel/scall32-o32.S
    +++ b/arch/mips/kernel/scall32-o32.S
    @@ -77,6 +77,18 @@ loads_done:
    PTR_WD load_a7, bad_stack_a7
    .previous

    + /*
    + * syscall number is in v0 unless we called syscall(__NR_###)
    + * where the real syscall number is in a0
    + */
    + subu t2, v0, __NR_O32_Linux
    + bnez t2, 1f /* __NR_syscall at offset 0 */
    + LONG_S a0, TI_SYSCALL($28) # Save a0 as syscall number
    + b 2f
    +1:
    + LONG_S v0, TI_SYSCALL($28) # Save v0 as syscall number
    +2:
    +
    lw t0, TI_FLAGS($28) # syscall tracing enabled?
    li t1, _TIF_WORK_SYSCALL_ENTRY
    and t0, t1
    @@ -114,16 +126,7 @@ syscall_trace_entry:
    SAVE_STATIC
    move a0, sp

    - /*
    - * syscall number is in v0 unless we called syscall(__NR_###)
    - * where the real syscall number is in a0
    - */
    - move a1, v0
    - subu t2, v0, __NR_O32_Linux
    - bnez t2, 1f /* __NR_syscall at offset 0 */
    - lw a1, PT_R4(sp)
    -
    -1: jal syscall_trace_enter
    + jal syscall_trace_enter

    bltz v0, 1f # seccomp failed? Skip syscall

    diff --git a/arch/mips/kernel/scall64-n32.S b/arch/mips/kernel/scall64-n32.S
    index 97456b2ca7dc3..97788859238c3 100644
    --- a/arch/mips/kernel/scall64-n32.S
    +++ b/arch/mips/kernel/scall64-n32.S
    @@ -44,6 +44,8 @@ NESTED(handle_sysn32, PT_SIZE, sp)

    sd a3, PT_R26(sp) # save a3 for syscall restarting

    + LONG_S v0, TI_SYSCALL($28) # Store syscall number
    +
    li t1, _TIF_WORK_SYSCALL_ENTRY
    LONG_L t0, TI_FLAGS($28) # syscall tracing enabled?
    and t0, t1, t0
    @@ -72,7 +74,6 @@ syscall_common:
    n32_syscall_trace_entry:
    SAVE_STATIC
    move a0, sp
    - move a1, v0
    jal syscall_trace_enter

    bltz v0, 1f # seccomp failed? Skip syscall
    diff --git a/arch/mips/kernel/scall64-n64.S b/arch/mips/kernel/scall64-n64.S
    index e6264aa62e457..be11ea5cc67e0 100644
    --- a/arch/mips/kernel/scall64-n64.S
    +++ b/arch/mips/kernel/scall64-n64.S
    @@ -46,6 +46,8 @@ NESTED(handle_sys64, PT_SIZE, sp)

    sd a3, PT_R26(sp) # save a3 for syscall restarting

    + LONG_S v0, TI_SYSCALL($28) # Store syscall number
    +
    li t1, _TIF_WORK_SYSCALL_ENTRY
    LONG_L t0, TI_FLAGS($28) # syscall tracing enabled?
    and t0, t1, t0
    @@ -82,7 +84,6 @@ n64_syscall_exit:
    syscall_trace_entry:
    SAVE_STATIC
    move a0, sp
    - move a1, v0
    jal syscall_trace_enter

    bltz v0, 1f # seccomp failed? Skip syscall
    diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
    index d3c2616cba226..7a5abb73e5312 100644
    --- a/arch/mips/kernel/scall64-o32.S
    +++ b/arch/mips/kernel/scall64-o32.S
    @@ -79,6 +79,22 @@ loads_done:
    PTR_WD load_a7, bad_stack_a7
    .previous

    + /*
    + * absolute syscall number is in v0 unless we called syscall(__NR_###)
    + * where the real syscall number is in a0
    + * note: NR_syscall is the first O32 syscall but the macro is
    + * only defined when compiling with -mabi=32 (CONFIG_32BIT)
    + * therefore __NR_O32_Linux is used (4000)
    + */
    +
    + subu t2, v0, __NR_O32_Linux
    + bnez t2, 1f /* __NR_syscall at offset 0 */
    + LONG_S a0, TI_SYSCALL($28) # Save a0 as syscall number
    + b 2f
    +1:
    + LONG_S v0, TI_SYSCALL($28) # Save v0 as syscall number
    +2:
    +
    li t1, _TIF_WORK_SYSCALL_ENTRY
    LONG_L t0, TI_FLAGS($28) # syscall tracing enabled?
    and t0, t1, t0
    @@ -113,22 +129,7 @@ trace_a_syscall:
    sd a7, PT_R11(sp) # For indirect syscalls

    move a0, sp
    - /*
    - * absolute syscall number is in v0 unless we called syscall(__NR_###)
    - * where the real syscall number is in a0
    - * note: NR_syscall is the first O32 syscall but the macro is
    - * only defined when compiling with -mabi=32 (CONFIG_32BIT)
    - * therefore __NR_O32_Linux is used (4000)
    - */
    - .set push
    - .set reorder
    - subu t1, v0, __NR_O32_Linux
    - move a1, v0
    - bnez t1, 1f /* __NR_syscall at offset 0 */
    - ld a1, PT_R4(sp) /* Arg1 for __NR_syscall case */
    - .set pop
    -
    -1: jal syscall_trace_enter
    + jal syscall_trace_enter

    bltz v0, 1f # seccomp failed? Skip syscall

    --
    2.43.0

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