From: Liangyan liangyan.peng@linux.alibaba.com
commit e04527fefba6e4e66492f122cf8cc6314f3cf3bf upstream.
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.
CPU 0 CPU 1 ovl_set_redirect lookup_fast ovl_get_redirect __d_lookup dget_dlock //no lock protection here spin_lock(&dentry->d_lock) dentry->d_lockref.count++ dentry->d_lockref.count++
[ 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
Cc: stable@vger.kernel.org Fixes: a6c606551141 ("ovl: redirect on rename-dir") Signed-off-by: Liangyan liangyan.peng@linux.alibaba.com Reviewed-by: Joseph Qi joseph.qi@linux.alibaba.com Suggested-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/overlayfs/dir.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -850,8 +850,8 @@ static char *ovl_get_redirect(struct den
buflen -= thislen; memcpy(&buf[buflen], name, thislen); - tmp = dget_dlock(d->d_parent); spin_unlock(&d->d_lock); + tmp = dget_parent(d);
dput(d); d = tmp;