Messages in this thread | | | Date | Sat, 17 Apr 2021 00:09:14 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH v2] riscv/kprobe: Restore local irqflag if kprobe is cancelled |
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On Fri, 16 Apr 2021 16:27:31 +0800 Liao Chang <liaochang1@huawei.com> wrote:
> The execution of sys_read end up hitting a BUG_ON() in __find_get_block after > installing probe at sys_read via kprobe, the BUG message like the following: > > [ 65.708663] ------------[ cut here ]------------ > [ 65.709987] kernel BUG at fs/buffer.c:1251! > [ 65.711283] Kernel BUG [#1] > [ 65.712032] Modules linked in: > [ 65.712925] CPU: 0 PID: 51 Comm: sh Not tainted 5.12.0-rc4 #1 > [ 65.714407] Hardware name: riscv-virtio,qemu (DT) > [ 65.715696] epc : __find_get_block+0x218/0x2c8 > [ 65.716835] ra : __getblk_gfp+0x1c/0x4a > [ 65.717831] epc : ffffffe00019f11e ra : ffffffe00019f56a sp : ffffffe002437930 > [ 65.719553] gp : ffffffe000f06030 tp : ffffffe0015abc00 t0 : ffffffe00191e038 > [ 65.721290] t1 : ffffffe00191e038 t2 : 000000000000000a s0 : ffffffe002437960 > [ 65.723051] s1 : ffffffe00160ad00 a0 : ffffffe00160ad00 a1 : 000000000000012a > [ 65.724772] a2 : 0000000000000400 a3 : 0000000000000008 a4 : 0000000000000040 > [ 65.726545] a5 : 0000000000000000 a6 : ffffffe00191e000 a7 : 0000000000000000 > [ 65.728308] s2 : 000000000000012a s3 : 0000000000000400 s4 : 0000000000000008 > [ 65.730049] s5 : 000000000000006c s6 : ffffffe00240f800 s7 : ffffffe000f080a8 > [ 65.731802] s8 : 0000000000000001 s9 : 000000000000012a s10: 0000000000000008 > [ 65.733516] s11: 0000000000000008 t3 : 00000000000003ff t4 : 000000000000000f > [ 65.734434] t5 : 00000000000003ff t6 : 0000000000040000 > [ 65.734613] status: 0000000000000100 badaddr: 0000000000000000 cause: 0000000000000003 > [ 65.734901] Call Trace: > [ 65.735076] [<ffffffe00019f11e>] __find_get_block+0x218/0x2c8 > [ 65.735417] [<ffffffe00020017a>] __ext4_get_inode_loc+0xb2/0x2f6 > [ 65.735618] [<ffffffe000201b6c>] ext4_get_inode_loc+0x3a/0x8a > [ 65.735802] [<ffffffe000203380>] ext4_reserve_inode_write+0x2e/0x8c > [ 65.735999] [<ffffffe00020357a>] __ext4_mark_inode_dirty+0x4c/0x18e > [ 65.736208] [<ffffffe000206bb0>] ext4_dirty_inode+0x46/0x66 > [ 65.736387] [<ffffffe000192914>] __mark_inode_dirty+0x12c/0x3da > [ 65.736576] [<ffffffe000180dd2>] touch_atime+0x146/0x150 > [ 65.736748] [<ffffffe00010d762>] filemap_read+0x234/0x246 > [ 65.736920] [<ffffffe00010d834>] generic_file_read_iter+0xc0/0x114 > [ 65.737114] [<ffffffe0001f5d7a>] ext4_file_read_iter+0x42/0xea > [ 65.737310] [<ffffffe000163f2c>] new_sync_read+0xe2/0x15a > [ 65.737483] [<ffffffe000165814>] vfs_read+0xca/0xf2 > [ 65.737641] [<ffffffe000165bae>] ksys_read+0x5e/0xc8 > [ 65.737816] [<ffffffe000165c26>] sys_read+0xe/0x16 > [ 65.737973] [<ffffffe000003972>] ret_from_syscall+0x0/0x2 > [ 65.738858] ---[ end trace fe93f985456c935d ]--- > > A simple reproducer looks like: > echo 'p:myprobe sys_read fd=%a0 buf=%a1 count=%a2' > /sys/kernel/debug/tracing/kprobe_events > echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable > cat trace > > Here's what happens to hit that BUG_ON(): > > If instruction being single stepped caused page fault, the > kprobe is cancelled to let the page fault handler continues > as normal page fault. But the local irqflags are disabled, > so CPU will restore 'sstatus' with 'SIE' masked. After page > fault is serviced, the kprobe is triggered again, we overwrite > the saved irqflag by calling kprobe_save_local_irqflag(). Note, > 'SIE' is masked in this new saved irqflag. After kprobe is > serviced, the CPU 'sstatus' is restored with 'SIE' masked. > This overwritten 'sstatus' cause BUG_ON() in __find_get_block. > > This bug is already fixed on arm64 by Jisheng Zhang. > > Fixes: c22b0bcb1dd02 ("riscv: Add kprobes supported") > Signed-off-by: Liao Chang <liaochang1@huawei.com>
Looks good to me.
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Thank you,
> --- > > Changes in v2: > - Reorganize commit message. > > arch/riscv/kernel/probes/kprobes.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c > index 7e2c78e2ca6b..d71f7c49a721 100644 > --- a/arch/riscv/kernel/probes/kprobes.c > +++ b/arch/riscv/kernel/probes/kprobes.c > @@ -260,8 +260,10 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr) > > if (kcb->kprobe_status == KPROBE_REENTER) > restore_previous_kprobe(kcb); > - else > + else { > + kprobes_restore_local_irqflag(kcb, regs); > reset_current_kprobe(); > + } > > break; > case KPROBE_HIT_ACTIVE: > -- > 2.17.1 >
-- Masami Hiramatsu <mhiramat@kernel.org>
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