[Devel] [PATCH RHEL9 COMMIT] dm-ploop: null pointer dereference in ploop_put_delta()

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.0-427.77.1.vz9.86.x-ovz" and will appear at git at bitbucket.org:openvz/vzkernel.git
after rh9-5.14.0-427.77.1.vz9.86.12
------>
commit fc7c8c0cf18c0d6c3a6f48bd940aefa0d1e797ed
Author: Vasileios Almpanis <vasileios.almpanis at virtuozzo.com>
Date:   Thu Oct 9 14:47:57 2025 +0000

    dm-ploop: null pointer dereference in ploop_put_delta()
    
    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 it by using IS_ERR() to properly detect error pointers from file_clone_open()
    
    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 | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-ploop-bat.c b/drivers/md/dm-ploop-bat.c
index a0b678b30b973..495d164d145f3 100644
--- a/drivers/md/dm-ploop-bat.c
+++ b/drivers/md/dm-ploop-bat.c
@@ -480,6 +480,7 @@ int ploop_add_delta(struct ploop *ploop, u32 level, struct file *file, bool is_r
 {
 	struct ploop_delta *deltas = ploop->deltas;
 	struct rb_root md_root = RB_ROOT;
+	struct file *cloned_file = NULL;
 	loff_t file_size;
 	u32 nr_be;
 	int ret, i;
@@ -510,11 +511,12 @@ int ploop_add_delta(struct ploop *ploop, u32 level, struct file *file, bool is_r
 		goto out;
 	}
 	for (i = 0; i < ploop->nkt_runners; i++) {
-		deltas[level].mtfile[i] = file_clone_open(file);
-		if (!deltas[level].mtfile[i]) {
-			ret = ENOMEM;
+		cloned_file = file_clone_open(file);
+		if (IS_ERR(cloned_file)) {
+			ret = PTR_ERR(cloned_file);
 			goto out;
 		}
+		deltas[level].mtfile[i] = cloned_file;
 	}
 	deltas[level].file_size = file_size;
 	deltas[level].file_preallocated_area_start = file_size;