On Tue, 9 Jun 2020 at 23:35, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > From: Oleg Nesterov <oleg@xxxxxxxxxx> > > commit 013b2deba9a6b80ca02f4fafd7dedf875e9b4450 upstream. > > uprobe_write_opcode() must not cross page boundary; prepare_uprobe() > relies on arch_uprobe_analyze_insn() which should validate "vaddr" but > some architectures (csky, s390, and sparc) don't do this. > > We can remove the BUG_ON() check in prepare_uprobe() and validate the > offset early in __uprobe_register(). The new IS_ALIGNED() check matches > the alignment check in arch_prepare_kprobe() on supported architectures, > so I think that all insns must be aligned to UPROBE_SWBP_INSN_SIZE. > > Another problem is __update_ref_ctr() which was wrong from the very > beginning, it can read/write outside of kmap'ed page unless "vaddr" is > aligned to sizeof(short), __uprobe_register() should check this too. > > Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> > Reviewed-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> > Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx> > Tested-by: Sven Schnelle <svens@xxxxxxxxxxxxx> > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > --- > kernel/events/uprobes.c | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) > > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -612,10 +612,6 @@ static int prepare_uprobe(struct uprobe > if (ret) > goto out; > > - /* uprobe_write_opcode() assumes we don't cross page boundary */ > - BUG_ON((uprobe->offset & ~PAGE_MASK) + > - UPROBE_SWBP_INSN_SIZE > PAGE_SIZE); > - > smp_wmb(); /* pairs with the smp_rmb() in handle_swbp() */ > set_bit(UPROBE_COPY_INSN, &uprobe->flags); > > @@ -911,6 +907,15 @@ static int __uprobe_register(struct inod > if (offset > i_size_read(inode)) > return -EINVAL; > > + /* > + * This ensures that copy_from_page(), copy_to_page() and > + * __update_ref_ctr() can't cross page boundary. > + */ > + if (!IS_ALIGNED(offset, UPROBE_SWBP_INSN_SIZE)) > + return -EINVAL; > + if (!IS_ALIGNED(ref_ctr_offset, sizeof(short))) stable-rc 4.19 build failure for x86_64, i386 and arm. make -sk KBUILD_BUILD_USER=TuxBuild -C/linux -j16 ARCH=x86 HOSTCC=gcc CC="sccache gcc" O=build 75 # 76 In file included from ../kernel/events/uprobes.c:25: 77 ../kernel/events/uprobes.c: In function ‘__uprobe_register’: 78 ../kernel/events/uprobes.c:916:18: error: ‘ref_ctr_offset’ undeclared (first use in this function); did you mean ‘per_cpu_offset’? 79 916 | if (!IS_ALIGNED(ref_ctr_offset, sizeof(short))) 80 | ^~~~~~~~~~~~~~ 81 ../include/linux/kernel.h:62:30: note: in definition of macro ‘IS_ALIGNED’ 82 62 | #define IS_ALIGNED(x, a) (((x) & ((typeof(x))(a) - 1)) == 0) 83 | ^ 84 ../kernel/events/uprobes.c:916:18: note: each undeclared identifier is reported only once for each function it appears in 85 916 | if (!IS_ALIGNED(ref_ctr_offset, sizeof(short))) 86 | ^~~~~~~~~~~~~~ 87 ../include/linux/kernel.h:62:30: note: in definition of macro ‘IS_ALIGNED’ 88 62 | #define IS_ALIGNED(x, a) (((x) & ((typeof(x))(a) - 1)) == 0) 89 | ^ 90 make[3]: *** [../scripts/Makefile.build:304: kernel/events/uprobes.o] Error 1 -- Linaro LKFT https://lkft.linaro.org
