| Message ID | 20250224031149.1598949-1-tongtiangen@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [-next,v3] uprobes: reject the share zeropage in uprobe_write_opcode() | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 9372bfd0e8fc..ca1879c74158 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -506,6 +506,11 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, if (ret <= 0) goto put_old; + if (is_zero_page(old_page)) { + ret = -EINVAL; + goto put_old; + } + if (WARN(!is_register && PageCompound(old_page), "uprobe unregister should never work on compound page\n")) { ret = -EINVAL;
We triggered the following error logs in syzkaller test: BUG: Bad page state in process syz.7.38 pfn:1eff3 page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1eff3 flags: 0x3fffff00004004(referenced|reserved|node=0|zone=1|lastcpupid=0x1fffff) raw: 003fffff00004004 ffffe6c6c07bfcc8 ffffe6c6c07bfcc8 0000000000000000 raw: 0000000000000000 0000000000000000 00000000fffffffe 0000000000000000 page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x32/0x50 bad_page+0x69/0xf0 free_unref_page_prepare+0x401/0x500 free_unref_page+0x6d/0x1b0 uprobe_write_opcode+0x460/0x8e0 install_breakpoint.part.0+0x51/0x80 register_for_each_vma+0x1d9/0x2b0 __uprobe_register+0x245/0x300 bpf_uprobe_multi_link_attach+0x29b/0x4f0 link_create+0x1e2/0x280 __sys_bpf+0x75f/0xac0 __x64_sys_bpf+0x1a/0x30 do_syscall_64+0x56/0x100 entry_SYSCALL_64_after_hwframe+0x78/0xe2 BUG: Bad rss-counter state mm:00000000452453e0 type:MM_FILEPAGES val:-1 The following syzkaller test case can be used to reproduce: r2 = creat(&(0x7f0000000000)='./file0\x00', 0x8) write$nbd(r2, &(0x7f0000000580)=ANY=[], 0x10) r4 = openat(0xffffffffffffff9c, &(0x7f0000000040)='./file0\x00', 0x42, 0x0) mmap$IORING_OFF_SQ_RING(&(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x0, 0x12, r4, 0x0) r5 = userfaultfd(0x80801) ioctl$UFFDIO_API(r5, 0xc018aa3f, &(0x7f0000000040)={0xaa, 0x20}) r6 = userfaultfd(0x80801) ioctl$UFFDIO_API(r6, 0xc018aa3f, &(0x7f0000000140)) ioctl$UFFDIO_REGISTER(r6, 0xc020aa00, &(0x7f0000000100)={{&(0x7f0000ffc000/0x4000)=nil, 0x4000}, 0x2}) ioctl$UFFDIO_ZEROPAGE(r5, 0xc020aa04, &(0x7f0000000000)={{&(0x7f0000ffd000/0x1000)=nil, 0x1000}}) r7 = bpf$PROG_LOAD(0x5, &(0x7f0000000140)={0x2, 0x3, &(0x7f0000000200)=ANY=[@ANYBLOB="1800000000120000000000000000000095"], &(0x7f0000000000)='GPL\x00', 0x7, 0x0, 0x0, 0x0, 0x0, '\x00', 0x0, @fallback=0x30, 0xffffffffffffffff, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x10, 0x0, @void, @value}, 0x94) bpf$BPF_LINK_CREATE_XDP(0x1c, &(0x7f0000000040)={r7, 0x0, 0x30, 0x1e, @val=@uprobe_multi={&(0x7f0000000080)='./file0\x00', &(0x7f0000000100)=[0x2], 0x0, 0x0, 0x1}}, 0x40) The cause is that zero pfn is set to the pte without increasing the rss count in mfill_atomic_pte_zeropage() and the refcount of zero folio does not increase accordingly. Then, the operation on the same pfn is performed in uprobe_write_opcode()->__replace_page() to unconditional decrease the rss count and old_folio's refcount. Therefore, two bugs are introduced: 1. The rss count is incorrect, when process exit, the check_mm() report error "Bad rss-count". 2. The reserved folio (zero folio) is freed when folio->refcount is zero, then free_pages_prepare->free_page_is_bad() report error "Bad page state". There is more, the following warn could also theoretically be triggered: __replace_page() -> ... -> folio_remove_rmap_pte() -> VM_WARN_ON_FOLIO(is_zero_folio(folio), folio) Considering that uprobe hit the zero folio is a very rare scene, just reject zero old folio immediately after get_user_page_vma_remote(). Fixes: 7396fa818d62 ("uprobes/core: Make background page replacement logic account for rss_stat counters") Fixes: 2b1444983508 ("uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints") Signed-off-by: Tong Tiangen <tongtiangen@huawei.com> Reviewed-by: David Hildenbrand <david@redhat.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> --- v3: update the subject/changelog as David suggests. v2: Modified according to the comments of David and Oleg. --- kernel/events/uprobes.c | 5 +++++ 1 file changed, 5 insertions(+)