On Thu, Feb 14, 2019 at 08:04:18AM -0500, Steven Rostedt wrote: > On Thu, 14 Feb 2019 08:05:24 +0800 > Changbin Du <changbin.du@xxxxxxxxx> wrote: > > > On Wed, Feb 13, 2019 at 10:41:43AM -0500, Steven Rostedt wrote: > > > On Wed, 13 Feb 2019 22:36:40 +0800 > > > Changbin Du <changbin.du@xxxxxxxxx> wrote: > > > > > > > Hi Steven, > > > > I think this is a critical issue. Could you give priority to this fix? > > > > > > > > On Fri, Jan 25, 2019 at 11:10:50PM +0800, Changbin Du wrote: > > > > > The userspace can ask kprobe to intercept strings at any memory address, > > > > > including invalid kernel address. In this case, fetch_store_strlen() > > > > > would crash since it uses general usercopy function. > > > > > > > > > > For example, we can crash the kernel by doing something as below: > > > > > > > > > > $ sudo kprobe 'p:do_sys_open +0(+0(%si)):string' > > > > > > Note, I'm not able to reproduce this. > > > > > > I just get: > > > > > > sendmail-1085 [001] .... 277.344573: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > <...>-1550 [003] .... 279.879011: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > <...>-1550 [003] .... 279.879056: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > <...>-1550 [003] .... 279.879079: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > <...>-1550 [003] .... 279.879132: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > <...>-1550 [003] .... 279.879683: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > <...>-1550 [003] .... 279.881521: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > <...>-1550 [003] .... 279.881541: open: (do_sys_open+0x0/0x210) arg1="" > > > <...>-1597 [005] .... 280.907662: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > <...>-1597 [005] .... 280.907694: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > <...>-1597 [005] .... 280.907772: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > <...>-1597 [005] .... 280.907825: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > <...>-1597 [005] .... 280.907891: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > <...>-1597 [005] .... 280.907947: open: (do_sys_open+0x0/0x210) arg1=(fault) > > > > > > > > > > > > > > > > [ 103.620391] BUG: GPF in non-whitelisted uaccess (non-canonical address?) > > > > > [ 103.622104] general protection fault: 0000 [#1] SMP PTI > > > > > [ 103.623424] CPU: 10 PID: 1046 Comm: cat Not tainted 5.0.0-rc3-00130-gd73aba1-dirty #96 > > > > > [ 103.625321] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-2-g628b2e6-dirty-20190104_103505-linux 04/01/2014 > > > > > [ 103.628284] RIP: 0010:process_fetch_insn+0x1ab/0x4b0 > > > > > > What line number is the RIP on? > > > > > I still can reproduce this bug on mainline (1f947a7a011fcceb14cb912f5481a53b18f1879a). > > But it seems your linux has already fix this issue. > > > No I didn't have the fix. I was running an older kernel actually. One > before commit 9da3f2b74054406f87dff7101a569217ffceb29b was added. > There's nothing actually wrong with that code, since kprobes is allowed > to poke at anything. But that commit considers the kernel using copy > from user to poke kernel address space is a security bug. > Glade to know that. And I wonder wether all such cases have been disclosed. I noticed the uprobe code also uses some usercopy functions. > So yeah, I agree your patch should be added with a stable tag, with a > Fixes: with that commit, since that commit is what causes it to bug. > > I'll apply it and start testing it. > > -- Steve -- Cheers, Changbin Du
