[PATCH v2] ovl: fix dentry leak in ovl_get_redirect
From: Liangyan
Date: Sun Dec 20 2020 - 07:12:55 EST
We need to lock d_parent->d_lock before dget_dlock, or this may
have d_lockref updated parallelly like calltrace below which will
cause dentry->d_lockref leak and risk a crash.
npm-20576 [028] .... 5705749.040094:
[28] ovl_set_redirect+0x11c/0x310 //tmp = dget_dlock(d->d_parent);
[28]? ovl_set_redirect+0x5/0x310
[28] ovl_rename+0x4db/0x790 [overlay]
[28] vfs_rename+0x6e8/0x920
[28] do_renameat2+0x4d6/0x560
[28] __x64_sys_rename+0x1c/0x20
[28] do_syscall_64+0x55/0x1a0
[28] entry_SYSCALL_64_after_hwframe+0x44/0xa9
npm-20574 [036] .... 5705749.040094:
[36] __d_lookup+0x107/0x140 //dentry->d_lockref.count++;
[36] lookup_fast+0xe0/0x2d0
[36] walk_component+0x48/0x350
[36] link_path_walk+0x1bf/0x650
[36]? path_init+0x1f6/0x2f0
[36] path_lookupat+0x82/0x210
[36] filename_lookup+0xb8/0x1a0
[36]? __audit_getname+0xa2/0xb0
[36]? getname_flags+0xb9/0x1e0
[36]? vfs_statx+0x73/0xe0
[36] vfs_statx+0x73/0xe0
[36] __do_sys_statx+0x3b/0x80
[36]? syscall_trace_enter+0x1ae/0x2c0
[36] do_syscall_64+0x55/0x1a0
[36] entry_SYSCALL_64_
[ 49.799059] PGD 800000061fed7067 P4D 800000061fed7067 PUD 61fec5067 PMD 0
[ 49.799689] Oops: 0002 [#1] SMP PTI
[ 49.800019] CPU: 2 PID: 2332 Comm: node Not tainted 4.19.24-7.20.al7.x86_64 #1
[ 49.800678] Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS 8a46cfe 04/01/2014
[ 49.801380] RIP: 0010:_raw_spin_lock+0xc/0x20
[ 49.803470] RSP: 0018:ffffac6fc5417e98 EFLAGS: 00010246
[ 49.803949] RAX: 0000000000000000 RBX: ffff93b8da3446c0 RCX: 0000000a00000000
[ 49.804600] RDX: 0000000000000001 RSI: 000000000000000a RDI: 0000000000000088
[ 49.805252] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff993cf040
[ 49.805898] R10: ffff93b92292e580 R11: ffffd27f188a4b80 R12: 0000000000000000
[ 49.806548] R13: 00000000ffffff9c R14: 00000000fffffffe R15: ffff93b8da3446c0
[ 49.807200] FS: 00007ffbedffb700(0000) GS:ffff93b927880000(0000) knlGS:0000000000000000
[ 49.807935] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 49.808461] CR2: 0000000000000088 CR3: 00000005e3f74006 CR4: 00000000003606a0
[ 49.809113] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 49.809758] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 49.810410] Call Trace:
[ 49.810653] d_delete+0x2c/0xb0
[ 49.810951] vfs_rmdir+0xfd/0x120
[ 49.811264] do_rmdir+0x14f/0x1a0
[ 49.811573] do_syscall_64+0x5b/0x190
[ 49.811917] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 49.812385] RIP: 0033:0x7ffbf505ffd7
[ 49.814404] RSP: 002b:00007ffbedffada8 EFLAGS: 00000297 ORIG_RAX: 0000000000000054
[ 49.815098] RAX: ffffffffffffffda RBX: 00007ffbedffb640 RCX: 00007ffbf505ffd7
[ 49.815744] RDX: 0000000004449700 RSI: 0000000000000000 RDI: 0000000006c8cd50
[ 49.816394] RBP: 00007ffbedffaea0 R08: 0000000000000000 R09: 0000000000017d0b
[ 49.817038] R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000012
[ 49.817687] R13: 00000000072823d8 R14: 00007ffbedffb700 R15: 00000000072823d8
[ 49.818338] Modules linked in: pvpanic cirrusfb button qemu_fw_cfg atkbd libps2 i8042
[ 49.819052] CR2: 0000000000000088
[ 49.819368] ---[ end trace 4e652b8aa299aa2d ]---
[ 49.819796] RIP: 0010:_raw_spin_lock+0xc/0x20
[ 49.821880] RSP: 0018:ffffac6fc5417e98 EFLAGS: 00010246
[ 49.822363] RAX: 0000000000000000 RBX: ffff93b8da3446c0 RCX: 0000000a00000000
[ 49.823008] RDX: 0000000000000001 RSI: 000000000000000a RDI: 0000000000000088
[ 49.823658] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff993cf040
[ 49.825404] R10: ffff93b92292e580 R11: ffffd27f188a4b80 R12: 0000000000000000
[ 49.827147] R13: 00000000ffffff9c R14: 00000000fffffffe R15: ffff93b8da3446c0
[ 49.828890] FS: 00007ffbedffb700(0000) GS:ffff93b927880000(0000) knlGS:0000000000000000
[ 49.830725] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 49.832359] CR2: 0000000000000088 CR3: 00000005e3f74006 CR4: 00000000003606a0
[ 49.834085] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 49.835792] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Fixes: a6c606551141 ("ovl: redirect on rename-dir")
Signed-off-by: Liangyan <liangyan.peng@xxxxxxxxxxxxxxxxx>
Suggested-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
---
fs/overlayfs/dir.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 28a075b5f5b2..a78d35017371 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -973,6 +973,7 @@ static char *ovl_get_redirect(struct dentry *dentry, bool abs_redirect)
for (d = dget(dentry); !IS_ROOT(d);) {
const char *name;
int thislen;
+ struct dentry *parent = NULL;
spin_lock(&d->d_lock);
name = ovl_dentry_get_redirect(d);
@@ -992,7 +993,22 @@ static char *ovl_get_redirect(struct dentry *dentry, bool abs_redirect)
buflen -= thislen;
memcpy(&buf[buflen], name, thislen);
- tmp = dget_dlock(d->d_parent);
+ parent = d->d_parent;
+ if (unlikely(!spin_trylock(&parent->d_lock))) {
+ rcu_read_lock();
+ spin_unlock(&d->d_lock);
+again:
+ parent = READ_ONCE(d->d_parent);
+ spin_lock(&parent->d_lock);
+ if (unlikely(parent != d->d_parent)) {
+ spin_unlock(&parent->d_lock);
+ goto again;
+ }
+ rcu_read_unlock();
+ spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
+ }
+ tmp = dget_dlock(parent);
+ spin_unlock(&parent->d_lock);
spin_unlock(&d->d_lock);
dput(d);
--
2.14.4.44.g2045bb6