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authorJohannes Berg <johannes.berg@intel.com>2021-01-14 00:08:02 +0300
committerRichard Weinberger <richard@nod.at>2021-02-12 23:31:08 +0300
commit47da29763ec9a153b9b685bff9db659e4e09e494 (patch)
tree05481f2a307bd8f7b5ded345b24c196dbf883302 /arch/um
parente1e22d0d9183aaaf65acf0cb529cb51ddbc12e08 (diff)
downloadlinux-47da29763ec9a153b9b685bff9db659e4e09e494.tar.xz
um: mm: check more comprehensively for stub changes
If userspace tries to change the stub, we need to kill it, because otherwise it can escape the virtual machine. In a few cases the stub checks weren't good, e.g. if userspace just tries to mmap(0x100000 - 0x1000, 0x3000, ...) it could succeed to get a new private/anonymous mapping replacing the stubs. Fix this by checking everywhere, and checking for _overlap_, not just direct changes. Cc: stable@vger.kernel.org Fixes: 3963333fe676 ("uml: cover stubs with a VMA") Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: Richard Weinberger <richard@nod.at>
Diffstat (limited to 'arch/um')
-rw-r--r--arch/um/kernel/tlb.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/arch/um/kernel/tlb.c b/arch/um/kernel/tlb.c
index 61776790cd67..89468da6bf88 100644
--- a/arch/um/kernel/tlb.c
+++ b/arch/um/kernel/tlb.c
@@ -125,6 +125,9 @@ static int add_mmap(unsigned long virt, unsigned long phys, unsigned long len,
struct host_vm_op *last;
int fd = -1, ret = 0;
+ if (virt + len > STUB_START && virt < STUB_END)
+ return -EINVAL;
+
if (hvc->userspace)
fd = phys_mapping(phys, &offset);
else
@@ -162,7 +165,7 @@ static int add_munmap(unsigned long addr, unsigned long len,
struct host_vm_op *last;
int ret = 0;
- if ((addr >= STUB_START) && (addr < STUB_END))
+ if (addr + len > STUB_START && addr < STUB_END)
return -EINVAL;
if (hvc->index != 0) {
@@ -192,6 +195,9 @@ static int add_mprotect(unsigned long addr, unsigned long len,
struct host_vm_op *last;
int ret = 0;
+ if (addr + len > STUB_START && addr < STUB_END)
+ return -EINVAL;
+
if (hvc->index != 0) {
last = &hvc->ops[hvc->index - 1];
if ((last->type == MPROTECT) &&
@@ -472,6 +478,10 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long address)
struct mm_id *mm_id;
address &= PAGE_MASK;
+
+ if (address >= STUB_START && address < STUB_END)
+ goto kill;
+
pgd = pgd_offset(mm, address);
if (!pgd_present(*pgd))
goto kill;