[PATCH 5.19 055/717] riscv: vdso: fix NULL deference in vdso_join_timens() when vfork

Greg Kroah-Hartman
2022-10-22T07:40:09Z

From: Jisheng Zhang <jszhang@kernel.org>

commit a8616d2dc193b6becc36b5f3cfeaa9ac7a5762f9 upstream.

Testing tools/testing/selftests/timens/vfork_exec.c got below
kernel log:

[ 6.838454] Unable to handle kernel access to user memory without uaccess routines at virtual address 0000000000000020
[ 6.842255] Oops [#1]
[ 6.842871] Modules linked in:
[ 6.844249] CPU: 1 PID: 64 Comm: vfork_exec Not tainted 6.0.0-rc3-rt15+ #8
[ 6.845861] Hardware name: riscv-virtio,qemu (DT)
[ 6.848009] epc : vdso_join_timens+0xd2/0x110
[ 6.850097] ra : vdso_join_timens+0xd2/0x110
[ 6.851164] epc : ffffffff8000635c ra : ffffffff8000635c sp : ff6000000181fbf0
[ 6.852562] gp : ffffffff80cff648 tp : ff60000000fdb700 t0 : 3030303030303030
[ 6.853852] t1 : 0000000000000030 t2 : 3030303030303030 s0 : ff6000000181fc40
[ 6.854984] s1 : ff60000001e6c000 a0 : 0000000000000010 a1 : ffffffff8005654c
[ 6.856221] a2 : 00000000ffffefff a3 : 0000000000000000 a4 : 0000000000000000
[ 6.858114] a5 : 0000000000000000 a6 : 0000000000000008 a7 : 0000000000000038
[ 6.859484] s2 : ff60000001e6c068 s3 : ff6000000108abb0 s4 : 0000000000000000
[ 6.860751] s5 : 0000000000001000 s6 : ffffffff8089dc40 s7 : ffffffff8089dc38
[ 6.862029] s8 : ffffffff8089dc30 s9 : ff60000000fdbe38 s10: 000000000000005e
[ 6.863304] s11: ffffffff80cc3510 t3 : ffffffff80d1112f t4 : ffffffff80d1112f
[ 6.864565] t5 : ffffffff80d11130 t6 : ff6000000181fa00
[ 6.865561] status: 0000000000000120 badaddr: 0000000000000020 cause: 000000000000000d
[ 6.868046] [<ffffffff8008dc94>] timens_commit+0x38/0x11a
[ 6.869089] [<ffffffff8008dde8>] timens_on_fork+0x72/0xb4
[ 6.870055] [<ffffffff80190096>] begin_new_exec+0x3c6/0x9f0
[ 6.871231] [<ffffffff801d826c>] load_elf_binary+0x628/0x1214
[ 6.872304] [<ffffffff8018ee7a>] bprm_execve+0x1f2/0x4e4
[ 6.873243] [<ffffffff8018f90c>] do_execveat_common+0x16e/0x1ee
[ 6.874258] [<ffffffff8018f9c8>] sys_execve+0x3c/0x48
[ 6.875162] [<ffffffff80003556>] ret_from_syscall+0x0/0x2
[ 6.877484] ---[ end trace 0000000000000000 ]---

This is because the mm->context.vdso_info is NULL in vfork case. From
another side, mm->context.vdso_info either points to vdso info
for RV64 or vdso info for compat, there's no need to bloat riscv's
mm_context_t, we can handle the difference when setup the additional
page for vdso.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Suggested-by: Palmer Dabbelt <palmer@rivosinc.com>
Fixes: 3092eb456375 ("riscv: compat: vdso: Add setup additional pages implementation")
Link: https://lore.kernel.org/r/20220924070737.3048-1-jszhang@kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/riscv/include/asm/mmu.h | 1 -
arch/riscv/kernel/vdso.c | 13 ++++++++++---
2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/include/asm/mmu.h b/arch/riscv/include/asm/mmu.h
index cedcf8ea3c76..0099dc116168 100644
--- a/arch/riscv/include/asm/mmu.h
+++ b/arch/riscv/include/asm/mmu.h
@@ -16,7 +16,6 @@ typedef struct {
atomic_long_t id;
#endif
void *vdso;
- void *vdso_info;
#ifdef CONFIG_SMP
/* A local icache flush is needed before user execution can resume. */
cpumask_t icache_stale_mask;
diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
index 69b05b6c181b..4abc9aebdfae 100644
--- a/arch/riscv/kernel/vdso.c
+++ b/arch/riscv/kernel/vdso.c
@@ -60,6 +60,11 @@ struct __vdso_info {
struct vm_special_mapping *cm;
};

+static struct __vdso_info vdso_info;
+#ifdef CONFIG_COMPAT
+static struct __vdso_info compat_vdso_info;
+#endif
+
static int vdso_mremap(const struct vm_special_mapping *sm,
struct vm_area_struct *new_vma)
{
@@ -114,15 +119,18 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
{
struct mm_struct *mm = task->mm;
struct vm_area_struct *vma;
- struct __vdso_info *vdso_info = mm->context.vdso_info;

mmap_read_lock(mm);

for (vma = mm->mmap; vma; vma = vma->vm_next) {
unsigned long size = vma->vm_end - vma->vm_start;

- if (vma_is_special_mapping(vma, vdso_info->dm))
+ if (vma_is_special_mapping(vma, vdso_info.dm))
zap_page_range(vma, vma->vm_start, size);
+#ifdef CONFIG_COMPAT
+ if (vma_is_special_mapping(vma, compat_vdso_info.dm))
+ zap_page_range(vma, vma->vm_start, size);
+#endif
}

mmap_read_unlock(mm);
@@ -264,7 +272,6 @@ static int __setup_additional_pages(struct mm_struct *mm,

vdso_base += VVAR_SIZE;
mm->context.vdso = (void *)vdso_base;
- mm->context.vdso_info = (void *)vdso_info;

ret =
_install_special_mapping(mm, vdso_base, vdso_text_len,
--
2.38.0