@@ -708,6 +708,7 @@ static int mmap_zero(struct file *file, struct vm_area_struct *vma)
#endif
if (vma->vm_flags & VM_SHARED)
return shmem_zero_setup(vma);
+ vma_set_anonymous(vma);
return 0;
}
@@ -293,6 +293,7 @@ static int __bprm_mm_init(struct linux_binprm *bprm)
bprm->vma = vma = vm_area_alloc(mm);
if (!vma)
return -ENOMEM;
+ vma_set_anonymous(vma);
if (down_write_killable(&mm->mmap_sem)) {
err = -EINTR;
@@ -454,10 +454,18 @@ struct vm_operations_struct {
static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
{
+ static const struct vm_operations_struct dummy_vm_ops = {};
+
vma->vm_mm = mm;
+ vma->vm_ops = &dummy_vm_ops;
INIT_LIST_HEAD(&vma->anon_vma_chain);
}
+static inline void vma_set_anonymous(struct vm_area_struct *vma)
+{
+ vma->vm_ops = NULL;
+}
+
struct mmu_gather;
struct inode;
@@ -1778,6 +1778,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
error = shmem_zero_setup(vma);
if (error)
goto free_vma;
+ } else {
+ vma_set_anonymous(vma);
}
vma_link(mm, vma, prev, rb_link, rb_parent);
@@ -2983,6 +2985,7 @@ static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long fla
return -ENOMEM;
}
+ vma_set_anonymous(vma);
vma->vm_start = addr;
vma->vm_end = addr + len;
vma->vm_pgoff = pgoff;
@@ -1145,6 +1145,8 @@ static int do_mmap_private(struct vm_area_struct *vma,
if (ret < len)
memset(base + ret, 0, len - ret);
+ } else {
+ vma_set_anonymous(vma);
}
return 0;
vma_is_anonymous() relies on ->vm_ops being NULL to detect anonymous VMA. This is unreliable as ->mmap may not set ->vm_ops. False-positive vma_is_anonymous() may lead to crashes: next ffff8801ce5e7040 prev ffff8801d20eca50 mm ffff88019c1e13c0 prot 27 anon_vma ffff88019680cdd8 vm_ops 0000000000000000 pgoff 0 file ffff8801b2ec2d00 private_data 0000000000000000 flags: 0xff(read|write|exec|shared|mayread|maywrite|mayexec|mayshare) ------------[ cut here ]------------ kernel BUG at mm/memory.c:1422! invalid opcode: 0000 [#1] SMP KASAN CPU: 0 PID: 18486 Comm: syz-executor3 Not tainted 4.18.0-rc3+ #136 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:zap_pmd_range mm/memory.c:1421 [inline] RIP: 0010:zap_pud_range mm/memory.c:1466 [inline] RIP: 0010:zap_p4d_range mm/memory.c:1487 [inline] RIP: 0010:unmap_page_range+0x1c18/0x2220 mm/memory.c:1508 Code: ff 31 ff 4c 89 e6 42 c6 04 33 f8 e8 92 dd d0 ff 4d 85 e4 0f 85 4a eb ff ff e8 54 dc d0 ff 48 8b bd 10 fc ff ff e8 82 95 fe ff <0f> 0b e8 41 dc d0 ff 0f 0b 4c 89 ad 18 fc ff ff c7 85 7c fb ff ff RSP: 0018:ffff8801b0587330 EFLAGS: 00010286 RAX: 000000000000013c RBX: 1ffff100360b0e9c RCX: ffffc90002620000 RDX: 0000000000000000 RSI: ffffffff81631851 RDI: 0000000000000001 RBP: ffff8801b05877c8 R08: ffff880199d40300 R09: ffffed003b5c4fc0 R10: ffffed003b5c4fc0 R11: ffff8801dae27e07 R12: 0000000000000000 R13: ffff88019c1e13c0 R14: dffffc0000000000 R15: 0000000020e01000 FS: 00007fca32251700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f04c540d000 CR3: 00000001ac1f0000 CR4: 00000000001426f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: unmap_single_vma+0x1a0/0x310 mm/memory.c:1553 zap_page_range_single+0x3cc/0x580 mm/memory.c:1644 unmap_mapping_range_vma mm/memory.c:2792 [inline] unmap_mapping_range_tree mm/memory.c:2813 [inline] unmap_mapping_pages+0x3a7/0x5b0 mm/memory.c:2845 unmap_mapping_range+0x48/0x60 mm/memory.c:2880 truncate_pagecache+0x54/0x90 mm/truncate.c:800 truncate_setsize+0x70/0xb0 mm/truncate.c:826 simple_setattr+0xe9/0x110 fs/libfs.c:409 notify_change+0xf13/0x10f0 fs/attr.c:335 do_truncate+0x1ac/0x2b0 fs/open.c:63 do_sys_ftruncate+0x492/0x560 fs/open.c:205 __do_sys_ftruncate fs/open.c:215 [inline] __se_sys_ftruncate fs/open.c:213 [inline] __x64_sys_ftruncate+0x59/0x80 fs/open.c:213 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe Reproducer: #include <stdio.h> #include <stddef.h> #include <stdint.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/stat.h> #include <sys/ioctl.h> #include <sys/mman.h> #include <unistd.h> #include <fcntl.h> #define KCOV_INIT_TRACE _IOR('c', 1, unsigned long) #define KCOV_ENABLE _IO('c', 100) #define KCOV_DISABLE _IO('c', 101) #define COVER_SIZE (1024<<10) #define KCOV_TRACE_PC 0 #define KCOV_TRACE_CMP 1 int main(int argc, char **argv) { int fd; unsigned long *cover; system("mount -t debugfs none /sys/kernel/debug"); fd = open("/sys/kernel/debug/kcov", O_RDWR); ioctl(fd, KCOV_INIT_TRACE, COVER_SIZE); cover = mmap(NULL, COVER_SIZE * sizeof(unsigned long), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); munmap(cover, COVER_SIZE * sizeof(unsigned long)); cover = mmap(NULL, COVER_SIZE * sizeof(unsigned long), PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0); memset(cover, 0, COVER_SIZE * sizeof(unsigned long)); ftruncate(fd, 3UL << 20); return 0; } This can be fixed by assigning anonymous VMAs own vm_ops and not relying on it being NULL. If ->mmap() failed to set ->vm_ops, mmap_region() will set it to dummy_vm_ops. This way we will have non-NULL ->vm_ops for all VMAs. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: syzbot+3f84280d52be9b7083cc@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> --- drivers/char/mem.c | 1 + fs/exec.c | 1 + include/linux/mm.h | 8 ++++++++ mm/mmap.c | 3 +++ mm/nommu.c | 2 ++ 5 files changed, 15 insertions(+)