6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Yang Erkun <yangerkun@xxxxxxxxxx>
[ Upstream commit f8c989a0c89a75d30f899a7cabdc14d72522bb8d ]
The last reference for `cache_head` can be reduced to zero in `c_show`
and `e_show`(using `rcu_read_lock` and `rcu_read_unlock`). Consequently,
`svc_export_put` and `expkey_put` will be invoked, leading to two
issues:
1. The `svc_export_put` will directly free ex_uuid. However,
`e_show`/`c_show` will access `ex_uuid` after `cache_put`, which can
trigger a use-after-free issue, shown below.
==================================================================
BUG: KASAN: slab-use-after-free in svc_export_show+0x362/0x430 [nfsd]
Read of size 1 at addr ff11000010fdc120 by task cat/870
CPU: 1 UID: 0 PID: 870 Comm: cat Not tainted 6.12.0-rc3+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.16.1-2.fc37 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x53/0x70
print_address_description.constprop.0+0x2c/0x3a0
print_report+0xb9/0x280
kasan_report+0xae/0xe0
svc_export_show+0x362/0x430 [nfsd]
c_show+0x161/0x390 [sunrpc]
seq_read_iter+0x589/0x770
seq_read+0x1e5/0x270
proc_reg_read+0xe1/0x140
vfs_read+0x125/0x530
ksys_read+0xc1/0x160
do_syscall_64+0x5f/0x170
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Allocated by task 830:
kasan_save_stack+0x20/0x40
kasan_save_track+0x14/0x30
__kasan_kmalloc+0x8f/0xa0
__kmalloc_node_track_caller_noprof+0x1bc/0x400
kmemdup_noprof+0x22/0x50
svc_export_parse+0x8a9/0xb80 [nfsd]
cache_do_downcall+0x71/0xa0 [sunrpc]
cache_write_procfs+0x8e/0xd0 [sunrpc]
proc_reg_write+0xe1/0x140
vfs_write+0x1a5/0x6d0
ksys_write+0xc1/0x160
do_syscall_64+0x5f/0x170
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Freed by task 868:
kasan_save_stack+0x20/0x40
kasan_save_track+0x14/0x30
kasan_save_free_info+0x3b/0x60
__kasan_slab_free+0x37/0x50
kfree+0xf3/0x3e0
svc_export_put+0x87/0xb0 [nfsd]
cache_purge+0x17f/0x1f0 [sunrpc]
nfsd_destroy_serv+0x226/0x2d0 [nfsd]
nfsd_svc+0x125/0x1e0 [nfsd]
write_threads+0x16a/0x2a0 [nfsd]
nfsctl_transaction_write+0x74/0xa0 [nfsd]
vfs_write+0x1a5/0x6d0
ksys_write+0xc1/0x160
do_syscall_64+0x5f/0x170
entry_SYSCALL_64_after_hwframe+0x76/0x7e
2. We cannot sleep while using `rcu_read_lock`/`rcu_read_unlock`.
However, `svc_export_put`/`expkey_put` will call path_put, which
subsequently triggers a sleeping operation due to the following
`dput`.
=============================
WARNING: suspicious RCU usage
5.10.0-dirty #141 Not tainted
-----------------------------
...
Call Trace:
dump_stack+0x9a/0xd0
___might_sleep+0x231/0x240
dput+0x39/0x600
path_put+0x1b/0x30
svc_export_put+0x17/0x80
e_show+0x1c9/0x200
seq_read_iter+0x63f/0x7c0
seq_read+0x226/0x2d0
vfs_read+0x113/0x2c0
ksys_read+0xc9/0x170
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x67/0xd1
Fix these issues by using `rcu_work` to help release
`svc_expkey`/`svc_export`. This approach allows for an asynchronous
context to invoke `path_put` and also facilitates the freeing of
`uuid/exp/key` after an RCU grace period.
Fixes: 9ceddd9da134 ("knfsd: Allow lockless lookups of the exports")
Signed-off-by: Yang Erkun <yangerkun@xxxxxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/nfsd/export.c | 31 +++++++++++++++++++++++++------
fs/nfsd/export.h | 4 ++--
2 files changed, 27 insertions(+), 8 deletions(-)
diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index c82d8e3e0d4f2..984f8e6379dd4 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -40,15 +40,24 @@
#define EXPKEY_HASHMAX (1 << EXPKEY_HASHBITS)
#define EXPKEY_HASHMASK (EXPKEY_HASHMAX -1)
-static void expkey_put(struct kref *ref)
+static void expkey_put_work(struct work_struct *work)
{
- struct svc_expkey *key = container_of(ref, struct svc_expkey, h.ref);
+ struct svc_expkey *key =
+ container_of(to_rcu_work(work), struct svc_expkey, ek_rcu_work);
if (test_bit(CACHE_VALID, &key->h.flags) &&
!test_bit(CACHE_NEGATIVE, &key->h.flags))
path_put(&key->ek_path);
auth_domain_put(key->ek_client);
- kfree_rcu(key, ek_rcu);
+ kfree(key);
+}
+
+static void expkey_put(struct kref *ref)
+{
+ struct svc_expkey *key = container_of(ref, struct svc_expkey, h.ref);
+
+ INIT_RCU_WORK(&key->ek_rcu_work, expkey_put_work);
+ queue_rcu_work(system_wq, &key->ek_rcu_work);
}
static int expkey_upcall(struct cache_detail *cd, struct cache_head *h)
@@ -355,16 +364,26 @@ static void export_stats_destroy(struct export_stats *stats)
EXP_STATS_COUNTERS_NUM);
}
-static void svc_export_put(struct kref *ref)
+static void svc_export_put_work(struct work_struct *work)
{
- struct svc_export *exp = container_of(ref, struct svc_export, h.ref);
+ struct svc_export *exp =
+ container_of(to_rcu_work(work), struct svc_export, ex_rcu_work);
+
path_put(&exp->ex_path);
auth_domain_put(exp->ex_client);
nfsd4_fslocs_free(&exp->ex_fslocs);
export_stats_destroy(exp->ex_stats);
kfree(exp->ex_stats);
kfree(exp->ex_uuid);
- kfree_rcu(exp, ex_rcu);
+ kfree(exp);
+}
+
+static void svc_export_put(struct kref *ref)
+{
+ struct svc_export *exp = container_of(ref, struct svc_export, h.ref);
+
+ INIT_RCU_WORK(&exp->ex_rcu_work, svc_export_put_work);
+ queue_rcu_work(system_wq, &exp->ex_rcu_work);
}
static int svc_export_upcall(struct cache_detail *cd, struct cache_head *h)
diff --git a/fs/nfsd/export.h b/fs/nfsd/export.h
index 3794ae253a701..081afb68681e1 100644
--- a/fs/nfsd/export.h
+++ b/fs/nfsd/export.h
@@ -75,7 +75,7 @@ struct svc_export {
u32 ex_layout_types;
struct nfsd4_deviceid_map *ex_devid_map;
struct cache_detail *cd;
- struct rcu_head ex_rcu;
+ struct rcu_work ex_rcu_work;
unsigned long ex_xprtsec_modes;
struct export_stats *ex_stats;
};
@@ -92,7 +92,7 @@ struct svc_expkey {
u32 ek_fsid[6];
struct path ek_path;
- struct rcu_head ek_rcu;
+ struct rcu_work ek_rcu_work;
};
#define EX_ISSYNC(exp) (!((exp)->ex_flags & NFSEXP_ASYNC))
--
2.43.0
