[syzbot] [fs?] KASAN: null-ptr-deref Write in do_pagemap_cmd

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 381f163531d8 Merge branch 'for-next/core' into for-kernelci
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=108175ac180000
kernel config: https://syzkaller.appspot.com/x/.config?x=2402d46ab3c7e581
dashboard link: https://syzkaller.appspot.com/bug?extid=02e64be5307d72e9c309
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1125fa6a180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1211e332180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/47402e75ee62/disk-381f1635.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a26a3a35fa67/vmlinux-381f1635.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d8dae1be1fa4/Image-381f1635.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+02e64b...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: null-ptr-deref in atomic_long_add_return_acquire include/linux/atomic/atomic-instrumented.h:3269 [inline]
BUG: KASAN: null-ptr-deref in rwsem_read_trylock kernel/locking/rwsem.c:243 [inline]
BUG: KASAN: null-ptr-deref in __down_read_common kernel/locking/rwsem.c:1249 [inline]
BUG: KASAN: null-ptr-deref in __down_read_killable kernel/locking/rwsem.c:1273 [inline]
BUG: KASAN: null-ptr-deref in down_read_killable+0x78/0x338 kernel/locking/rwsem.c:1551
Write of size 8 at addr 0000000000000120 by task syz-executor185/6171

CPU: 0 PID: 6171 Comm: syz-executor185 Tainted: G B 6.8.0-rc6-syzkaller-g381f163531d8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Call trace:
dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:291
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:298
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106
print_report+0xe4/0x518 mm/kasan/report.c:491
kasan_report+0xd8/0x138 mm/kasan/report.c:601
kasan_check_range+0x254/0x294 mm/kasan/generic.c:189
__kasan_check_write+0x20/0x30 mm/kasan/shadow.c:37
instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
atomic_long_add_return_acquire include/linux/atomic/atomic-instrumented.h:3269 [inline]
rwsem_read_trylock kernel/locking/rwsem.c:243 [inline]
__down_read_common kernel/locking/rwsem.c:1249 [inline]
__down_read_killable kernel/locking/rwsem.c:1273 [inline]
down_read_killable+0x78/0x338 kernel/locking/rwsem.c:1551
mmap_read_lock_killable include/linux/mmap_lock.h:155 [inline]
do_pagemap_scan fs/proc/task_mmu.c:2460 [inline]
do_pagemap_cmd+0x8d8/0x1240 fs/proc/task_mmu.c:2513
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl fs/ioctl.c:857 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:857
__invoke_syscall arch/arm64/kernel/syscall.c:34 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:48
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:133
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:152
el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
==================================================================
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000120
Mem abort info:
ESR = 0x0000000096000006
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000
CM = 0, WnR = 0, TnD = 0, TagAccess = 0
GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
user pgtable: 4k pages, 48-bit VAs, pgdp=00000001129c0000
[0000000000000120] pgd=080000011d13d003, p4d=080000011d13d003, pud=080000011cfae003, pmd=0000000000000000
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 6171 Comm: syz-executor185 Tainted: G B 6.8.0-rc6-syzkaller-g381f163531d8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __lse_atomic64_fetch_add_acquire arch/arm64/include/asm/atomic_lse.h:169 [inline]
pc : __lse_atomic64_add_return_acquire arch/arm64/include/asm/atomic_lse.h:202 [inline]
pc : arch_atomic64_add_return_acquire arch/arm64/include/asm/atomic.h:91 [inline]
pc : raw_atomic64_add_return_acquire include/linux/atomic/atomic-arch-fallback.h:2703 [inline]
pc : raw_atomic_long_add_return_acquire include/linux/atomic/atomic-long.h:163 [inline]
pc : atomic_long_add_return_acquire include/linux/atomic/atomic-instrumented.h:3270 [inline]
pc : rwsem_read_trylock kernel/locking/rwsem.c:243 [inline]
pc : __down_read_common kernel/locking/rwsem.c:1249 [inline]
pc : __down_read_killable kernel/locking/rwsem.c:1273 [inline]
pc : down_read_killable+0x80/0x338 kernel/locking/rwsem.c:1551
lr : instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
lr : atomic_long_add_return_acquire include/linux/atomic/atomic-instrumented.h:3269 [inline]
lr : rwsem_read_trylock kernel/locking/rwsem.c:243 [inline]
lr : __down_read_common kernel/locking/rwsem.c:1249 [inline]
lr : __down_read_killable kernel/locking/rwsem.c:1273 [inline]
lr : down_read_killable+0x78/0x338 kernel/locking/rwsem.c:1551
sp : ffff8000978a79d0
x29: ffff8000978a79d0 x28: ffff8000978a7b40 x27: dfff800000000000
x26: 0000000000000000 x25: 0000000020ffd000 x24: ffff8000978a7b68
x23: ffff700012f14f68 x22: ffff0000d8fdda2c x21: 0000000000000120
x20: 0000000000000190 x19: ffff800080cef5fc x18: 0000000000000000
x17: 3d3d3d3d3d3d3d3d x16: ffff800080275eb0 x15: 0000000000000001
x14: 1ffff000123e3a9c x13: 0000000000000000 x12: 0000000000000000
x11: ffff7000123e3a9d x10: 0000000000ff0100 x9 : 0000000000000000
x8 : 0000000000000100 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff8000978a71d8 x4 : ffff80008ed81760 x3 : ffff8000801c0944
x2 : 0000000000000001 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
raw_atomic64_add_return_acquire include/linux/atomic/atomic-arch-fallback.h:2703 [inline]
raw_atomic_long_add_return_acquire include/linux/atomic/atomic-long.h:163 [inline]
atomic_long_add_return_acquire include/linux/atomic/atomic-instrumented.h:3270 [inline]
rwsem_read_trylock kernel/locking/rwsem.c:243 [inline]
__down_read_common kernel/locking/rwsem.c:1249 [inline]
__down_read_killable kernel/locking/rwsem.c:1273 [inline]
down_read_killable+0x80/0x338 kernel/locking/rwsem.c:1551
mmap_read_lock_killable include/linux/mmap_lock.h:155 [inline]
do_pagemap_scan fs/proc/task_mmu.c:2460 [inline]
do_pagemap_cmd+0x8d8/0x1240 fs/proc/task_mmu.c:2513
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl fs/ioctl.c:857 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:857
__invoke_syscall arch/arm64/kernel/syscall.c:34 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:48
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:133
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:152
el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
Code: 52800101 974346ca d503201f 52802008 (f8a802a8)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 52800101 mov w1, #0x8 // #8
4: 974346ca bl 0xfffffffffd0d1b2c
8: d503201f nop
c: 52802008 mov w8, #0x100 // #256
* 10: f8a802a8 ldadda x8, x8, [x21] <-- trapping instruction


---
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[Edward Adam Davis]

please test null ptr deref in do_pagemap_cmd

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 3f78ebbb795f..ab28666956d0 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -2510,6 +2510,8 @@ static long do_pagemap_cmd(struct file *file, unsigned int cmd,

switch (cmd) {
case PAGEMAP_SCAN:
+ if (!mm)
+ return -EINVAL;
return do_pagemap_scan(mm, arg);

default:

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+02e64b...@syzkaller.appspotmail.com

Tested on:

commit: 90d35da6 Linux 6.8-rc7
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1279a07a180000
kernel config: https://syzkaller.appspot.com/x/.config?x=f7212ea23efeb053

dashboard link: https://syzkaller.appspot.com/bug?extid=02e64be5307d72e9c309
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

patch: https://syzkaller.appspot.com/x/patch.diff?x=1111146c180000

Note: testing is done by a robot and is best-effort only.

[Edward Adam Davis]

When pagemap_open() runs in the kernel thread context, task->mm is NULL, it will
causes the pagemap file object's file->private_date to be NULL when the pagemap
file is opened, this will ultimately result in do_pagemap_cmd() referencing a
null pointer.

So, before PAGEMAP_SCAN ioctl() call do_pagemap_scan(), need check mm first.

Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs")
Reported-and-tested-by: syzbot+02e64b...@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <ead...@qq.com>
---
fs/proc/task_mmu.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 3f78ebbb795f..ab28666956d0 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -2510,6 +2510,8 @@ static long do_pagemap_cmd(struct file *file, unsigned int cmd,

switch (cmd) {
case PAGEMAP_SCAN:
+ if (!mm)
+ return -EINVAL;
return do_pagemap_scan(mm, arg);

default:

--
2.43.0