[Devel] [PATCH vz9/vz10] dm-ploop: null pointer dereference in ploop_put_delta()

[Vasileios Almpanis]

The ploop_add_delta() function calls file_clone_open() to create multiple
file handles, but only checks for NULL return values. However,
file_clone_open() can return ERR_PTR() on failure, which gets stored as
a corrupted file pointer in deltas[level].mtfile[i].

Later, during cleanup in ploop_put_delta(), fput() is called on these
corrupted pointers , causing the kernel to attempt accessing invalid 
memory addresses resulting in NULL pointer dereference crashes.

  BUG: kernel NULL pointer dereference, address: 0000000000000034
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] PREEMPT SMP PTI
  CPU: 6 PID: 274635 Comm: dmsetup ve: / Kdump: loaded Tainted: G               X  -------  ---  5.14.0-427.77.1.vz9.86.12 #1 86.12
  Hardware name: Supermicro SYS-5039MS-H12NR/X11SSE-F, BIOS 2.3 12/12/2019
  RIP: 0010:fput_many+0x7/0x90
  RSP: 0018:ffffa55e45ab3bd0 EFLAGS: 00010286
  RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: 0000000000000001 RDI: fffffffffffffffc
  RBP: ffff8aaf304a2800 R08: ffff8aaebbc83800 R09: 20c49ba5e353f7cf
  R10: ffff8aaec85428f0 R11: ffffffffc05c41fc R12: ffff8aaf287d9f40
  R13: ffff8aaf28692000 R14: 0000000000000004 R15: 0000000000000003
  FS:  00007feb47a0d840(0000) GS:ffff8abc77b80000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000000034 CR3: 0000000323e94003 CR4: 00000000003706e0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   <TASK>
   ? show_trace_log_lvl+0x1c4/0x2df
   ? show_trace_log_lvl+0x1c4/0x2df
   ? ploop_put_delta+0x51/0x76 [ploop]
   ? __die_body.cold+0x8/0xd
   ? page_fault_oops+0x134/0x170
   ? exc_page_fault+0x62/0x150
   ? asm_exc_page_fault+0x22/0x30
   ? fuse_generic_request_alloc+0x1c/0x80 [fuse]
   ? fput_many+0x7/0x90
   ploop_put_delta+0x51/0x76 [ploop]
   ploop_destroy+0x17b/0x2a0 [ploop]
   dm_table_destroy+0x59/0x120 [dm_mod]
   dev_remove+0xdb/0x1a0 [dm_mod]
   ctl_ioctl+0x1a5/0x290 [dm_mod]
   dm_ctl_ioctl+0xa/0x20 [dm_mod]
   __x64_sys_ioctl+0x87/0xc0
   do_syscall_64+0x59/0x90
   ? syscall_exit_work+0x103/0x130
   ? syscall_exit_to_user_mode+0x19/0x40
   ? do_syscall_64+0x69/0x90
   ? exit_to_user_mode_loop+0xd0/0x130
   ? exit_to_user_mode_prepare+0xb6/0x100
   ? syscall_exit_to_user_mode+0x19/0x40
   ? do_syscall_64+0x69/0x90
   ? do_user_addr_fault+0x1d6/0x6a0
   ? syscall_exit_work+0x103/0x130
   ? exc_page_fault+0x62/0x150
   entry_SYSCALL_64_after_hwframe+0x77/0xe1
  RIP: 0033:0x7feb4783ec6b
  RSP: 002b:00007ffdc8dc7c98 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
  RAX: ffffffffffffffda RBX: 00007feb47c0fbd0 RCX: 00007feb4783ec6b
  RDX: 00005651f9b00c80 RSI: 00000000c138fd04 RDI: 0000000000000003
  RBP: 00007feb47c4c316 R08: 00007feb47c4f2d8 R09: 00007ffdc8dc7af0
  R10: 00007feb47c4c316 R11: 0000000000000206 R12: 00005651f9b00c80
  R13: 00005651f9b00d30 R14: 00007feb47c4c316 R15: 00005651f9b00a00
   </TASK>
  CR2: 0000000000000034

Fix by:
1. Using IS_ERR() to properly detect error pointers from file_clone_open()
2. Adding IS_ERR() checks in ploop_put_delta() to prevent cleanup crashes
3. Setting failed mtfile entries to NULL to avoid double-free issues

https://virtuozzo.atlassian.net/browse/VSTOR-116965
Signed-off-by: Vasileios Almpanis <vasileios.almpanis at virtuozzo.com>

Feature: dm-ploop: ploop target driver

---
 drivers/md/dm-ploop-bat.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-ploop-bat.c b/drivers/md/dm-ploop-bat.c
index a0b678b30b97..65c74960f29c 100644
--- a/drivers/md/dm-ploop-bat.c
+++ b/drivers/md/dm-ploop-bat.c
@@ -511,8 +511,9 @@ int ploop_add_delta(struct ploop *ploop, u32 level, struct file *file, bool is_r
 	}
 	for (i = 0; i < ploop->nkt_runners; i++) {
 		deltas[level].mtfile[i] = file_clone_open(file);
-		if (!deltas[level].mtfile[i]) {
-			ret = ENOMEM;
+		if (IS_ERR(deltas[level].mtfile[i])) {
+			ret = PTR_ERR(deltas[level].mtfile[i]);
+			deltas[level].mtfile[i] = NULL;
 			goto out;
 		}
 	}
@@ -531,14 +532,14 @@ void ploop_put_delta(struct ploop *ploop, struct ploop_delta *delta)
 {
 	int i;
 
-	if (delta->file) {
+	if (delta->file && !IS_ERR(delta->file)) {
 		vfs_fsync(delta->file, 1);
 		fput(delta->file);
 	}
 
 	if (delta->mtfile) {
 		for (i = 0; i < ploop->nkt_runners; i++) {
-			if (delta->mtfile[i])
+			if (delta->mtfile[i] && !IS_ERR(delta->mtfile[i]))
 				fput(delta->mtfile[i]);
 		}
 		kfree(delta->mtfile);
-- 
2.43.0