* [PATCH] nfs: callback_proc: fix an incorrect NULL check on list iterator
@ 2022-03-27 8:02 Xiaomeng Tong
2022-03-27 15:20 ` Trond Myklebust
0 siblings, 1 reply; 6+ messages in thread
From: Xiaomeng Tong @ 2022-03-27 8:02 UTC (permalink / raw)
To: trond.myklebust, anna
Cc: bhalevy, bharrosh, linux-nfs, linux-kernel, Xiaomeng Tong, stable
The bug is here:
if (!server ||
server->pnfs_curr_ld->id != dev->cbd_layout_type) {
The list iterator value 'server' will *always* be set and non-NULL
by list_for_each_entry_rcu, so it is incorrect to assume that the
iterator value will be NULL if the list is empty or no element is
found (In fact, it will be a bogus pointer to an invalid struct
object containing the HEAD, which is used for above check at next
outer loop). Otherwise it may bypass the check in theory (iif
server->pnfs_curr_ld->id == dev->cbd_layout_type, 'server' now is
a bogus pointer) and lead to invalid memory access passing the check.
To fix the bug, use a new variable 'iter' as the list iterator,
while use the original variable 'server' as a dedicated pointer to
point to the found element.
Cc: stable@vger.kernel.org
Fixes: 1be5683b03a76 ("pnfs: CB_NOTIFY_DEVICEID")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
---
fs/nfs/callback_proc.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index c343666d9a42..84779785dc8d 100644
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -361,7 +361,7 @@ __be32 nfs4_callback_devicenotify(void *argp, void *resp,
uint32_t i;
__be32 res = 0;
struct nfs_client *clp = cps->clp;
- struct nfs_server *server = NULL;
+ struct nfs_server *server = NULL, *iter;
if (!clp) {
res = cpu_to_be32(NFS4ERR_OP_NOT_IN_SESSION);
@@ -374,10 +374,11 @@ __be32 nfs4_callback_devicenotify(void *argp, void *resp,
if (!server ||
server->pnfs_curr_ld->id != dev->cbd_layout_type) {
rcu_read_lock();
- list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
- if (server->pnfs_curr_ld &&
- server->pnfs_curr_ld->id == dev->cbd_layout_type) {
+ list_for_each_entry_rcu(iter, &clp->cl_superblocks, client_link)
+ if (iter->pnfs_curr_ld &&
+ iter->pnfs_curr_ld->id == dev->cbd_layout_type) {
rcu_read_unlock();
+ server = iter;
goto found;
}
rcu_read_unlock();
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] nfs: callback_proc: fix an incorrect NULL check on list iterator 2022-03-27 8:02 [PATCH] nfs: callback_proc: fix an incorrect NULL check on list iterator Xiaomeng Tong @ 2022-03-27 15:20 ` Trond Myklebust 2022-03-28 1:43 ` Xiaomeng Tong 0 siblings, 1 reply; 6+ messages in thread From: Trond Myklebust @ 2022-03-27 15:20 UTC (permalink / raw) To: anna, xiam0nd.tong; +Cc: bhalevy, linux-nfs, stable, linux-kernel, bharrosh On Sun, 2022-03-27 at 16:02 +0800, Xiaomeng Tong wrote: > The bug is here: > if (!server || > server->pnfs_curr_ld->id != dev->cbd_layout_type) { > > The list iterator value 'server' will *always* be set and non-NULL > by list_for_each_entry_rcu, so it is incorrect to assume that the > iterator value will be NULL if the list is empty or no element is > found (In fact, it will be a bogus pointer to an invalid struct > object containing the HEAD, which is used for above check at next > outer loop). Otherwise it may bypass the check in theory (iif > server->pnfs_curr_ld->id == dev->cbd_layout_type, 'server' now is > a bogus pointer) and lead to invalid memory access passing the check. > > To fix the bug, use a new variable 'iter' as the list iterator, > while use the original variable 'server' as a dedicated pointer to > point to the found element. > > Cc: stable@vger.kernel.org > Fixes: 1be5683b03a76 ("pnfs: CB_NOTIFY_DEVICEID") > Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com> > --- > fs/nfs/callback_proc.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c > index c343666d9a42..84779785dc8d 100644 > --- a/fs/nfs/callback_proc.c > +++ b/fs/nfs/callback_proc.c > @@ -361,7 +361,7 @@ __be32 nfs4_callback_devicenotify(void *argp, > void *resp, > uint32_t i; > __be32 res = 0; > struct nfs_client *clp = cps->clp; > - struct nfs_server *server = NULL; > + struct nfs_server *server = NULL, *iter; > > if (!clp) { > res = cpu_to_be32(NFS4ERR_OP_NOT_IN_SESSION); > @@ -374,10 +374,11 @@ __be32 nfs4_callback_devicenotify(void *argp, > void *resp, > if (!server || > server->pnfs_curr_ld->id != dev->cbd_layout_type) > { > rcu_read_lock(); > - list_for_each_entry_rcu(server, &clp- > >cl_superblocks, client_link) > - if (server->pnfs_curr_ld && > - server->pnfs_curr_ld->id == dev- > >cbd_layout_type) { > + list_for_each_entry_rcu(iter, &clp- > >cl_superblocks, client_link) > + if (iter->pnfs_curr_ld && > + iter->pnfs_curr_ld->id == dev- > >cbd_layout_type) { > rcu_read_unlock(); > + server = iter; Hmm... We're not holding any locks on the super block for 'iter' here, so nothing is preventing it from going away while we're. Given that we really only want a pointer to the struct pnfs_layoutdriver_type anyway, why not just convert the code to save a pointer to that (and do it while holding the rcu_read_lock())? The struct pnfs_layoutdriver is always expected to be a statically allocated structure, so it won't go away as long as the pNFS driver module remains loaded. > goto found; > } > rcu_read_unlock(); -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.myklebust@hammerspace.com ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] nfs: callback_proc: fix an incorrect NULL check on list iterator 2022-03-27 15:20 ` Trond Myklebust @ 2022-03-28 1:43 ` Xiaomeng Tong 2022-03-28 13:24 ` Trond Myklebust 0 siblings, 1 reply; 6+ messages in thread From: Xiaomeng Tong @ 2022-03-28 1:43 UTC (permalink / raw) To: trondmy Cc: anna, bhalevy, bharrosh, linux-kernel, linux-nfs, stable, xiam0nd.tong On Sun, 27 Mar 2022 15:20:42 +0000, Trond Myklebust wrote: > On Sun, 2022-03-27 at 16:02 +0800, Xiaomeng Tong wrote: > > The bug is here: > > if (!server || > > server->pnfs_curr_ld->id != dev->cbd_layout_type) { > > > > The list iterator value 'server' will *always* be set and non-NULL > > by list_for_each_entry_rcu, so it is incorrect to assume that the > > iterator value will be NULL if the list is empty or no element is > > found (In fact, it will be a bogus pointer to an invalid struct > > object containing the HEAD, which is used for above check at next > > outer loop). Otherwise it may bypass the check in theory (iif > > server->pnfs_curr_ld->id == dev->cbd_layout_type, 'server' now is > > a bogus pointer) and lead to invalid memory access passing the check. > > > > To fix the bug, use a new variable 'iter' as the list iterator, > > while use the original variable 'server' as a dedicated pointer to > > point to the found element. > > > > Cc: stable@vger.kernel.org > > Fixes: 1be5683b03a76 ("pnfs: CB_NOTIFY_DEVICEID") > > Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com> > > --- > > fs/nfs/callback_proc.c | 9 +++++---- > > 1 file changed, 5 insertions(+), 4 deletions(-) > > > > diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c > > index c343666d9a42..84779785dc8d 100644 > > --- a/fs/nfs/callback_proc.c > > +++ b/fs/nfs/callback_proc.c > > @@ -361,7 +361,7 @@ __be32 nfs4_callback_devicenotify(void *argp, > > void *resp, > > uint32_t i; > > __be32 res = 0; > > struct nfs_client *clp = cps->clp; > > - struct nfs_server *server = NULL; > > + struct nfs_server *server = NULL, *iter; > > > > if (!clp) { > > res = cpu_to_be32(NFS4ERR_OP_NOT_IN_SESSION); > > @@ -374,10 +374,11 @@ __be32 nfs4_callback_devicenotify(void *argp, > > void *resp, > > if (!server || > > server->pnfs_curr_ld->id != dev->cbd_layout_type) > > { > > rcu_read_lock(); > > - list_for_each_entry_rcu(server, &clp- > > >cl_superblocks, client_link) > > - if (server->pnfs_curr_ld && > > - server->pnfs_curr_ld->id == dev- > > >cbd_layout_type) { > > + list_for_each_entry_rcu(iter, &clp- > > >cl_superblocks, client_link) > > + if (iter->pnfs_curr_ld && > > + iter->pnfs_curr_ld->id == dev- > > >cbd_layout_type) { > > rcu_read_unlock(); > > + server = iter; > > Hmm... We're not holding any locks on the super block for 'iter' here, > so nothing is preventing it from going away while we're. > ok, i am not a 'rcu lock' expert, i will make it hold the rcu_read_lock() if necessary. > Given that we really only want a pointer to the struct > pnfs_layoutdriver_type anyway, why not just convert the code to save a > pointer to that (and do it while holding the rcu_read_lock())? > Maybe it's not that simple. If you only save a pointer to that and still use 'server' as the list iterator of list_for_each_entry_rcu, there could be problem. I.e., if no element found in list_for_each_entry_rcu in the first outer 'for' loop, and now 'server' is a bogus pointer to an invalid struct, and continue to go into the second outer 'for' loop, and the check below will lead to invalid memory access (server->pnfs_curr_ld->id), even can potentialy be bypassed with crafted data to make the condition false and mistakely run nfs4_delete_deviceid(server->pnfs_curr_ld, clp, &dev->cbd_dev_id); with bogus 'server'. if (!server || server->pnfs_curr_ld->id != dev->cbd_layout_type) { > The struct pnfs_layoutdriver is always expected to be a statically > allocated structure, so it won't go away as long as the pNFS driver > module remains loaded. > -- Xiaomeng Tong ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] nfs: callback_proc: fix an incorrect NULL check on list iterator 2022-03-28 1:43 ` Xiaomeng Tong @ 2022-03-28 13:24 ` Trond Myklebust 2022-03-28 13:43 ` Greg KH 2022-03-29 4:00 ` Xiaomeng Tong 0 siblings, 2 replies; 6+ messages in thread From: Trond Myklebust @ 2022-03-28 13:24 UTC (permalink / raw) To: xiam0nd.tong; +Cc: anna, linux-nfs, stable, linux-kernel On Mon, 2022-03-28 at 09:43 +0800, Xiaomeng Tong wrote: > On Sun, 27 Mar 2022 15:20:42 +0000, Trond Myklebust wrote: > > On Sun, 2022-03-27 at 16:02 +0800, Xiaomeng Tong wrote: > > > The bug is here: > > > if (!server || > > > server->pnfs_curr_ld->id != dev->cbd_layout_type) { > > > > > > The list iterator value 'server' will *always* be set and non- > > > NULL > > > by list_for_each_entry_rcu, so it is incorrect to assume that the > > > iterator value will be NULL if the list is empty or no element is > > > found (In fact, it will be a bogus pointer to an invalid struct > > > object containing the HEAD, which is used for above check at next > > > outer loop). Otherwise it may bypass the check in theory (iif > > > server->pnfs_curr_ld->id == dev->cbd_layout_type, 'server' now is > > > a bogus pointer) and lead to invalid memory access passing the > > > check. > > > > > > To fix the bug, use a new variable 'iter' as the list iterator, > > > while use the original variable 'server' as a dedicated pointer > > > to > > > point to the found element. > > > > > > Cc: stable@vger.kernel.org > > > Fixes: 1be5683b03a76 ("pnfs: CB_NOTIFY_DEVICEID") > > > Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com> > > > --- > > > fs/nfs/callback_proc.c | 9 +++++---- > > > 1 file changed, 5 insertions(+), 4 deletions(-) > > > > > > diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c > > > index c343666d9a42..84779785dc8d 100644 > > > --- a/fs/nfs/callback_proc.c > > > +++ b/fs/nfs/callback_proc.c > > > @@ -361,7 +361,7 @@ __be32 nfs4_callback_devicenotify(void *argp, > > > void *resp, > > > uint32_t i; > > > __be32 res = 0; > > > struct nfs_client *clp = cps->clp; > > > - struct nfs_server *server = NULL; > > > + struct nfs_server *server = NULL, *iter; > > > > > > if (!clp) { > > > res = cpu_to_be32(NFS4ERR_OP_NOT_IN_SESSION); > > > @@ -374,10 +374,11 @@ __be32 nfs4_callback_devicenotify(void > > > *argp, > > > void *resp, > > > if (!server || > > > server->pnfs_curr_ld->id != dev- > > > >cbd_layout_type) > > > { > > > rcu_read_lock(); > > > - list_for_each_entry_rcu(server, &clp- > > > > cl_superblocks, client_link) > > > - if (server->pnfs_curr_ld && > > > - server->pnfs_curr_ld->id == > > > dev- > > > > cbd_layout_type) { > > > + list_for_each_entry_rcu(iter, &clp- > > > > cl_superblocks, client_link) > > > + if (iter->pnfs_curr_ld && > > > + iter->pnfs_curr_ld->id == > > > dev- > > > > cbd_layout_type) { > > > rcu_read_unlock(); > > > + server = iter; > > > > Hmm... We're not holding any locks on the super block for 'iter' > > here, > > so nothing is preventing it from going away while we're. > > > > ok, i am not a 'rcu lock' expert, i will make it hold the > rcu_read_lock() > if necessary. > > > Given that we really only want a pointer to the struct > > pnfs_layoutdriver_type anyway, why not just convert the code to > > save a > > pointer to that (and do it while holding the rcu_read_lock())? > > > > Maybe it's not that simple. If you only save a pointer to that and > still > use 'server' as the list iterator of list_for_each_entry_rcu, there > could > be problem. > > I.e., if no element found in list_for_each_entry_rcu in the first > outer > 'for' loop, and now 'server' is a bogus pointer to an invalid struct, > and > continue to go into the second outer 'for' loop, and the check below > will > lead to invalid memory access (server->pnfs_curr_ld->id), even can > potentialy > be bypassed with crafted data to make the condition false and > mistakely run > nfs4_delete_deviceid(server->pnfs_curr_ld, clp, &dev->cbd_dev_id); > with bogus > 'server'. > > if (!server || > server->pnfs_curr_ld->id != dev->cbd_layout_type) { > > > The struct pnfs_layoutdriver is always expected to be a statically > > allocated structure, so it won't go away as long as the pNFS driver > > module remains loaded. > Let's just do the following. 8<----------------------------------------------- From 7c9d845f0612e5bcd23456a2ec43be8ac43458f1 Mon Sep 17 00:00:00 2001 From: Trond Myklebust <trond.myklebust@hammerspace.com> Date: Mon, 28 Mar 2022 08:36:34 -0400 Subject: [PATCH] NFSv4/pNFS: Fix another issue with a list iterator pointing to the head In nfs4_callback_devicenotify(), if we don't find a matching entry for the deviceid, we're left with a pointer to 'struct nfs_server' that actually points to the list of super blocks associated with our struct nfs_client. Furthermore, even if we have a valid pointer, nothing pins the super block, and so the struct nfs_server could end up getting freed while we're using it. Since all we want is a pointer to the struct pnfs_layoutdriver_type, let's skip all the iteration over super blocks, and just use APIs to find the layout driver directly. Reported-by: Xiaomeng Tong <xiam0nd.tong@gmail.com> Fixes: 1be5683b03a7 ("pnfs: CB_NOTIFY_DEVICEID") Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> --- fs/nfs/callback_proc.c | 27 +++++++++------------------ fs/nfs/pnfs.c | 11 +++++++++++ fs/nfs/pnfs.h | 2 ++ 3 files changed, 22 insertions(+), 18 deletions(-) diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c index 39d1ec870d90..c8520284dda7 100644 --- a/fs/nfs/callback_proc.c +++ b/fs/nfs/callback_proc.c @@ -358,12 +358,11 @@ __be32 nfs4_callback_devicenotify(void *argp, void *resp, struct cb_process_state *cps) { struct cb_devicenotifyargs *args = argp; + const struct pnfs_layoutdriver_type *ld = NULL; uint32_t i; __be32 res = 0; - struct nfs_client *clp = cps->clp; - struct nfs_server *server = NULL; - if (!clp) { + if (!cps->clp) { res = cpu_to_be32(NFS4ERR_OP_NOT_IN_SESSION); goto out; } @@ -371,23 +370,15 @@ __be32 nfs4_callback_devicenotify(void *argp, void *resp, for (i = 0; i < args->ndevs; i++) { struct cb_devicenotifyitem *dev = &args->devs[i]; - if (!server || - server->pnfs_curr_ld->id != dev->cbd_layout_type) { - rcu_read_lock(); - list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) - if (server->pnfs_curr_ld && - server->pnfs_curr_ld->id == dev->cbd_layout_type) { - rcu_read_unlock(); - goto found; - } - rcu_read_unlock(); - continue; + if (!ld || ld->id != dev->cbd_layout_type) { + pnfs_put_layoutdriver(ld); + ld = pnfs_find_layoutdriver(dev->cbd_layout_type); + if (!ld) + continue; } - - found: - nfs4_delete_deviceid(server->pnfs_curr_ld, clp, &dev->cbd_dev_id); + nfs4_delete_deviceid(ld, cps->clp, &dev->cbd_dev_id); } - + pnfs_put_layoutdriver(ld); out: kfree(args->devs); return res; diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index de318bb5d349..856c962273c7 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -92,6 +92,17 @@ find_pnfs_driver(u32 id) return local; } +const struct pnfs_layoutdriver_type *pnfs_find_layoutdriver(u32 id) +{ + return find_pnfs_driver(id); +} + +void pnfs_put_layoutdriver(const struct pnfs_layoutdriver_type *ld) +{ + if (ld) + module_put(ld->owner); +} + void unset_pnfs_layoutdriver(struct nfs_server *nfss) { diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h index f4d7548d67b2..07f11489e4e9 100644 --- a/fs/nfs/pnfs.h +++ b/fs/nfs/pnfs.h @@ -234,6 +234,8 @@ struct pnfs_devicelist { extern int pnfs_register_layoutdriver(struct pnfs_layoutdriver_type *); extern void pnfs_unregister_layoutdriver(struct pnfs_layoutdriver_type *); +extern const struct pnfs_layoutdriver_type *pnfs_find_layoutdriver(u32 id); +extern void pnfs_put_layoutdriver(const struct pnfs_layoutdriver_type *ld); /* nfs4proc.c */ extern size_t max_response_pages(struct nfs_server *server); -- 2.35.1 -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.myklebust@hammerspace.com ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] nfs: callback_proc: fix an incorrect NULL check on list iterator 2022-03-28 13:24 ` Trond Myklebust @ 2022-03-28 13:43 ` Greg KH 2022-03-29 4:00 ` Xiaomeng Tong 1 sibling, 0 replies; 6+ messages in thread From: Greg KH @ 2022-03-28 13:43 UTC (permalink / raw) To: Trond Myklebust; +Cc: xiam0nd.tong, anna, linux-nfs, stable, linux-kernel On Mon, Mar 28, 2022 at 01:24:57PM +0000, Trond Myklebust wrote: > On Mon, 2022-03-28 at 09:43 +0800, Xiaomeng Tong wrote: > > On Sun, 27 Mar 2022 15:20:42 +0000, Trond Myklebust wrote: > > > On Sun, 2022-03-27 at 16:02 +0800, Xiaomeng Tong wrote: > > > > The bug is here: > > > > if (!server || > > > > server->pnfs_curr_ld->id != dev->cbd_layout_type) { > > > > > > > > The list iterator value 'server' will *always* be set and non- > > > > NULL > > > > by list_for_each_entry_rcu, so it is incorrect to assume that the > > > > iterator value will be NULL if the list is empty or no element is > > > > found (In fact, it will be a bogus pointer to an invalid struct > > > > object containing the HEAD, which is used for above check at next > > > > outer loop). Otherwise it may bypass the check in theory (iif > > > > server->pnfs_curr_ld->id == dev->cbd_layout_type, 'server' now is > > > > a bogus pointer) and lead to invalid memory access passing the > > > > check. > > > > > > > > To fix the bug, use a new variable 'iter' as the list iterator, > > > > while use the original variable 'server' as a dedicated pointer > > > > to > > > > point to the found element. > > > > > > > > Cc: stable@vger.kernel.org > > > > Fixes: 1be5683b03a76 ("pnfs: CB_NOTIFY_DEVICEID") > > > > Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com> > > > > --- > > > > fs/nfs/callback_proc.c | 9 +++++---- > > > > 1 file changed, 5 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c > > > > index c343666d9a42..84779785dc8d 100644 > > > > --- a/fs/nfs/callback_proc.c > > > > +++ b/fs/nfs/callback_proc.c > > > > @@ -361,7 +361,7 @@ __be32 nfs4_callback_devicenotify(void *argp, > > > > void *resp, > > > > uint32_t i; > > > > __be32 res = 0; > > > > struct nfs_client *clp = cps->clp; > > > > - struct nfs_server *server = NULL; > > > > + struct nfs_server *server = NULL, *iter; > > > > > > > > if (!clp) { > > > > res = cpu_to_be32(NFS4ERR_OP_NOT_IN_SESSION); > > > > @@ -374,10 +374,11 @@ __be32 nfs4_callback_devicenotify(void > > > > *argp, > > > > void *resp, > > > > if (!server || > > > > server->pnfs_curr_ld->id != dev- > > > > >cbd_layout_type) > > > > { > > > > rcu_read_lock(); > > > > - list_for_each_entry_rcu(server, &clp- > > > > > cl_superblocks, client_link) > > > > - if (server->pnfs_curr_ld && > > > > - server->pnfs_curr_ld->id == > > > > dev- > > > > > cbd_layout_type) { > > > > + list_for_each_entry_rcu(iter, &clp- > > > > > cl_superblocks, client_link) > > > > + if (iter->pnfs_curr_ld && > > > > + iter->pnfs_curr_ld->id == > > > > dev- > > > > > cbd_layout_type) { > > > > rcu_read_unlock(); > > > > + server = iter; > > > > > > Hmm... We're not holding any locks on the super block for 'iter' > > > here, > > > so nothing is preventing it from going away while we're. > > > > > > > ok, i am not a 'rcu lock' expert, i will make it hold the > > rcu_read_lock() > > if necessary. > > > > > Given that we really only want a pointer to the struct > > > pnfs_layoutdriver_type anyway, why not just convert the code to > > > save a > > > pointer to that (and do it while holding the rcu_read_lock())? > > > > > > > Maybe it's not that simple. If you only save a pointer to that and > > still > > use 'server' as the list iterator of list_for_each_entry_rcu, there > > could > > be problem. > > > > I.e., if no element found in list_for_each_entry_rcu in the first > > outer > > 'for' loop, and now 'server' is a bogus pointer to an invalid struct, > > and > > continue to go into the second outer 'for' loop, and the check below > > will > > lead to invalid memory access (server->pnfs_curr_ld->id), even can > > potentialy > > be bypassed with crafted data to make the condition false and > > mistakely run > > nfs4_delete_deviceid(server->pnfs_curr_ld, clp, &dev->cbd_dev_id); > > with bogus > > 'server'. > > > > if (!server || > > server->pnfs_curr_ld->id != dev->cbd_layout_type) { > > > > > The struct pnfs_layoutdriver is always expected to be a statically > > > allocated structure, so it won't go away as long as the pNFS driver > > > module remains loaded. > > > > > Let's just do the following. > > 8<----------------------------------------------- > From 7c9d845f0612e5bcd23456a2ec43be8ac43458f1 Mon Sep 17 00:00:00 2001 > From: Trond Myklebust <trond.myklebust@hammerspace.com> > Date: Mon, 28 Mar 2022 08:36:34 -0400 > Subject: [PATCH] NFSv4/pNFS: Fix another issue with a list iterator pointing > to the head > > In nfs4_callback_devicenotify(), if we don't find a matching entry for > the deviceid, we're left with a pointer to 'struct nfs_server' that > actually points to the list of super blocks associated with our struct > nfs_client. > Furthermore, even if we have a valid pointer, nothing pins the super > block, and so the struct nfs_server could end up getting freed while > we're using it. > > Since all we want is a pointer to the struct pnfs_layoutdriver_type, > let's skip all the iteration over super blocks, and just use APIs to > find the layout driver directly. > > Reported-by: Xiaomeng Tong <xiam0nd.tong@gmail.com> > Fixes: 1be5683b03a7 ("pnfs: CB_NOTIFY_DEVICEID") > Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> > --- > fs/nfs/callback_proc.c | 27 +++++++++------------------ > fs/nfs/pnfs.c | 11 +++++++++++ > fs/nfs/pnfs.h | 2 ++ > 3 files changed, 22 insertions(+), 18 deletions(-) <formletter> This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly. </formletter> ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] nfs: callback_proc: fix an incorrect NULL check on list iterator 2022-03-28 13:24 ` Trond Myklebust 2022-03-28 13:43 ` Greg KH @ 2022-03-29 4:00 ` Xiaomeng Tong 1 sibling, 0 replies; 6+ messages in thread From: Xiaomeng Tong @ 2022-03-29 4:00 UTC (permalink / raw) To: trondmy; +Cc: anna, linux-kernel, linux-nfs, stable, xiam0nd.tong On Mon, 28 Mar 2022 13:24:57 +0000, Trond Myklebust wrote: > Let's just do the following. > > 8<----------------------------------------------- > From 7c9d845f0612e5bcd23456a2ec43be8ac43458f1 Mon Sep 17 00:00:00 2001 > From: Trond Myklebust <trond.myklebust@hammerspace.com> > Date: Mon, 28 Mar 2022 08:36:34 -0400 > Subject: [PATCH] NFSv4/pNFS: Fix another issue with a list iterator pointing > to the head > > In nfs4_callback_devicenotify(), if we don't find a matching entry for > the deviceid, we're left with a pointer to 'struct nfs_server' that > actually points to the list of super blocks associated with our struct > nfs_client. > Furthermore, even if we have a valid pointer, nothing pins the super > block, and so the struct nfs_server could end up getting freed while > we're using it. > > Since all we want is a pointer to the struct pnfs_layoutdriver_type, > let's skip all the iteration over super blocks, and just use APIs to > find the layout driver directly. > > Reported-by: Xiaomeng Tong <xiam0nd.tong@gmail.com> > Fixes: 1be5683b03a7 ("pnfs: CB_NOTIFY_DEVICEID") > Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> > --- > fs/nfs/callback_proc.c | 27 +++++++++------------------ > fs/nfs/pnfs.c | 11 +++++++++++ > fs/nfs/pnfs.h | 2 ++ > 3 files changed, 22 insertions(+), 18 deletions(-) > > diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c > index 39d1ec870d90..c8520284dda7 100644 > --- a/fs/nfs/callback_proc.c > +++ b/fs/nfs/callback_proc.c > @@ -358,12 +358,11 @@ __be32 nfs4_callback_devicenotify(void *argp, void *resp, > struct cb_process_state *cps) > { > struct cb_devicenotifyargs *args = argp; > + const struct pnfs_layoutdriver_type *ld = NULL; > uint32_t i; > __be32 res = 0; > - struct nfs_client *clp = cps->clp; > - struct nfs_server *server = NULL; > > - if (!clp) { > + if (!cps->clp) { > res = cpu_to_be32(NFS4ERR_OP_NOT_IN_SESSION); > goto out; > } > @@ -371,23 +370,15 @@ __be32 nfs4_callback_devicenotify(void *argp, void *resp, > for (i = 0; i < args->ndevs; i++) { > struct cb_devicenotifyitem *dev = &args->devs[i]; > > - if (!server || > - server->pnfs_curr_ld->id != dev->cbd_layout_type) { > - rcu_read_lock(); > - list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) > - if (server->pnfs_curr_ld && > - server->pnfs_curr_ld->id == dev->cbd_layout_type) { > - rcu_read_unlock(); > - goto found; > - } > - rcu_read_unlock(); > - continue; > + if (!ld || ld->id != dev->cbd_layout_type) { > + pnfs_put_layoutdriver(ld); > + ld = pnfs_find_layoutdriver(dev->cbd_layout_type); > + if (!ld) > + continue; > } > - > - found: > - nfs4_delete_deviceid(server->pnfs_curr_ld, clp, &dev->cbd_dev_id); > + nfs4_delete_deviceid(ld, cps->clp, &dev->cbd_dev_id); > } > - > + pnfs_put_layoutdriver(ld); > out: > kfree(args->devs); > return res; > diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c > index de318bb5d349..856c962273c7 100644 > --- a/fs/nfs/pnfs.c > +++ b/fs/nfs/pnfs.c > @@ -92,6 +92,17 @@ find_pnfs_driver(u32 id) > return local; > } > > +const struct pnfs_layoutdriver_type *pnfs_find_layoutdriver(u32 id) > +{ > + return find_pnfs_driver(id); > +} > + > +void pnfs_put_layoutdriver(const struct pnfs_layoutdriver_type *ld) > +{ > + if (ld) > + module_put(ld->owner); > +} > + > void > unset_pnfs_layoutdriver(struct nfs_server *nfss) > { > diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h > index f4d7548d67b2..07f11489e4e9 100644 > --- a/fs/nfs/pnfs.h > +++ b/fs/nfs/pnfs.h > @@ -234,6 +234,8 @@ struct pnfs_devicelist { > > extern int pnfs_register_layoutdriver(struct pnfs_layoutdriver_type *); > extern void pnfs_unregister_layoutdriver(struct pnfs_layoutdriver_type *); > +extern const struct pnfs_layoutdriver_type *pnfs_find_layoutdriver(u32 id); > +extern void pnfs_put_layoutdriver(const struct pnfs_layoutdriver_type *ld); > > /* nfs4proc.c */ > extern size_t max_response_pages(struct nfs_server *server); > -- Thank you, i have resend a PATCH v2 with fix as you suggested, and also with some changes, please check it. -- Xiaomeng Tong ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-03-29 4:00 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-03-27 8:02 [PATCH] nfs: callback_proc: fix an incorrect NULL check on list iterator Xiaomeng Tong 2022-03-27 15:20 ` Trond Myklebust 2022-03-28 1:43 ` Xiaomeng Tong 2022-03-28 13:24 ` Trond Myklebust 2022-03-28 13:43 ` Greg KH 2022-03-29 4:00 ` Xiaomeng Tong
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