| Message ID | 20210327140702.4916-1-ducheng2@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v2] net:qrtr: fix atomic idr allocation in qrtr_port_assign() | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Guessed tree name to be net-next |
| netdev/subject_prefix | warning | Target tree name not specified in the subject |
| netdev/cc_maintainers | warning | 8 maintainers not CCed: cjhuang@codeaurora.org wenhu.wang@vivo.com loic.poulain@linaro.org miaoqinglang@huawei.com necip@google.com xiyou.wangcong@gmail.com bjorn.andersson@linaro.org edumazet@google.com |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 3 this patch: 3 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 23 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 3 this patch: 3 |
| netdev/header_inline | success | Link |
Adding the xarray maintainer... On Sat, Mar 27, 2021 at 10:07:02PM +0800, Du Cheng wrote: > add idr_preload() and idr_preload_end() around idr_alloc_u32(GFP_ATOMIC) > due to internal use of per_cpu variables, which requires preemption > disabling/enabling. > > reported as "BUG: "using smp_processor_id() in preemptible" by syzkaller > > Reported-by: syzbot+3eec59e770685e3dc879@syzkaller.appspotmail.com > Signed-off-by: Du Cheng <ducheng2@gmail.com> > --- > changelog > v1: change to GFP_KERNEL for idr_alloc_u32() but might sleep > v2: revert to GFP_ATOMIC but add preemption disable/enable protection > > net/qrtr/qrtr.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c > index edb6ac17ceca..6361f169490e 100644 > --- a/net/qrtr/qrtr.c > +++ b/net/qrtr/qrtr.c > @@ -722,17 +722,23 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port) > mutex_lock(&qrtr_port_lock); > if (!*port) { > min_port = QRTR_MIN_EPH_SOCKET; > + idr_preload(GFP_ATOMIC); > rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, QRTR_MAX_EPH_SOCKET, GFP_ATOMIC); > + idr_preload_end(); This seems "odd" to me. We are asking idr_alloc_u32() to abide by GFP_ATOMIC, so why do we need to "preload" it with the same type of allocation? Is there something in the idr/radix/xarray code that can't really handle GFP_ATOMIC during a "normal" idr allocation that is causing this warning to be hit? Why is this change the "correct" one? thanks, greg k-h
On Sat, Mar 27, 2021 at 03:12:14PM +0100, Greg Kroah-Hartman wrote: > Adding the xarray maintainer... > > On Sat, Mar 27, 2021 at 10:07:02PM +0800, Du Cheng wrote: > > add idr_preload() and idr_preload_end() around idr_alloc_u32(GFP_ATOMIC) > > due to internal use of per_cpu variables, which requires preemption > > disabling/enabling. > > > > reported as "BUG: "using smp_processor_id() in preemptible" by syzkaller > > > > Reported-by: syzbot+3eec59e770685e3dc879@syzkaller.appspotmail.com > > Signed-off-by: Du Cheng <ducheng2@gmail.com> > > --- > > changelog > > v1: change to GFP_KERNEL for idr_alloc_u32() but might sleep > > v2: revert to GFP_ATOMIC but add preemption disable/enable protection > > > > net/qrtr/qrtr.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c > > index edb6ac17ceca..6361f169490e 100644 > > --- a/net/qrtr/qrtr.c > > +++ b/net/qrtr/qrtr.c > > @@ -722,17 +722,23 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port) > > mutex_lock(&qrtr_port_lock); > > if (!*port) { > > min_port = QRTR_MIN_EPH_SOCKET; > > + idr_preload(GFP_ATOMIC); > > rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, QRTR_MAX_EPH_SOCKET, GFP_ATOMIC); > > + idr_preload_end(); > > This seems "odd" to me. We are asking idr_alloc_u32() to abide by > GFP_ATOMIC, so why do we need to "preload" it with the same type of > allocation? > > Is there something in the idr/radix/xarray code that can't really handle > GFP_ATOMIC during a "normal" idr allocation that is causing this warning > to be hit? Why is this change the "correct" one? > > thanks, > > greg k-h From the comment above idr_preload() in lib/radix-tree.c:1460 /** * idr_preload - preload for idr_alloc() * @gfp_mask: allocation mask to use for preloading * * Preallocate memory to use for the next call to idr_alloc(). This function * returns with preemption disabled. It will be enabled by idr_preload_end(). */ idr_alloc is a very simple wrapper around idr_alloc_u32(). On top of radix_tree_node_alloc() which is called by idr_alloc_u32(), there is this comment at line 244 in the same radix-tree.c /* * This assumes that the caller has performed appropriate preallocation, and * that the caller has pinned this thread of control to the current CPU. */ Therefore the preload/preload_end are necessary, or at least should have preemption disabled Regards, Du Cheng
On Sat, Mar 27, 2021 at 10:25:20PM +0800, Du Cheng wrote: > On Sat, Mar 27, 2021 at 03:12:14PM +0100, Greg Kroah-Hartman wrote: > > Adding the xarray maintainer... > > > > On Sat, Mar 27, 2021 at 10:07:02PM +0800, Du Cheng wrote: > > > add idr_preload() and idr_preload_end() around idr_alloc_u32(GFP_ATOMIC) > > > due to internal use of per_cpu variables, which requires preemption > > > disabling/enabling. > > > > > > reported as "BUG: "using smp_processor_id() in preemptible" by syzkaller > > > > > > Reported-by: syzbot+3eec59e770685e3dc879@syzkaller.appspotmail.com > > > Signed-off-by: Du Cheng <ducheng2@gmail.com> > > > --- > > > changelog > > > v1: change to GFP_KERNEL for idr_alloc_u32() but might sleep > > > v2: revert to GFP_ATOMIC but add preemption disable/enable protection > > > > > > net/qrtr/qrtr.c | 6 ++++++ > > > 1 file changed, 6 insertions(+) > > > > > > diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c > > > index edb6ac17ceca..6361f169490e 100644 > > > --- a/net/qrtr/qrtr.c > > > +++ b/net/qrtr/qrtr.c > > > @@ -722,17 +722,23 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port) > > > mutex_lock(&qrtr_port_lock); > > > if (!*port) { > > > min_port = QRTR_MIN_EPH_SOCKET; > > > + idr_preload(GFP_ATOMIC); > > > rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, QRTR_MAX_EPH_SOCKET, GFP_ATOMIC); > > > + idr_preload_end(); > > > > This seems "odd" to me. We are asking idr_alloc_u32() to abide by > > GFP_ATOMIC, so why do we need to "preload" it with the same type of > > allocation? > > > > Is there something in the idr/radix/xarray code that can't really handle > > GFP_ATOMIC during a "normal" idr allocation that is causing this warning > > to be hit? Why is this change the "correct" one? > > > > thanks, > > > > greg k-h > > > >From the comment above idr_preload() in lib/radix-tree.c:1460 > /** > * idr_preload - preload for idr_alloc() > * @gfp_mask: allocation mask to use for preloading > * > * Preallocate memory to use for the next call to idr_alloc(). This function > * returns with preemption disabled. It will be enabled by idr_preload_end(). > */ > > idr_alloc is a very simple wrapper around idr_alloc_u32(). > > On top of radix_tree_node_alloc() which is called by idr_alloc_u32(), there is > this comment at line 244 in the same radix-tree.c > /* > * This assumes that the caller has performed appropriate preallocation, and > * that the caller has pinned this thread of control to the current CPU. > */ > > Therefore the preload/preload_end are necessary, or at least should have > preemption disabled Ah, so it's disabling preemption that is the key here. Still odd, why is GFP_ATOMIC not sufficient in a normal idr_alloc() call to keep things from doing stuff like this? Feels like a lot of "internal knowledge" is needed here to use this api properly... Matthew, is the above change really correct? thanks, greg k-h
On Sat, Mar 27, 2021 at 03:31:18PM +0100, Greg Kroah-Hartman wrote: > On Sat, Mar 27, 2021 at 10:25:20PM +0800, Du Cheng wrote: > > On Sat, Mar 27, 2021 at 03:12:14PM +0100, Greg Kroah-Hartman wrote: > > > Adding the xarray maintainer... > > > > > > On Sat, Mar 27, 2021 at 10:07:02PM +0800, Du Cheng wrote: > > > > add idr_preload() and idr_preload_end() around idr_alloc_u32(GFP_ATOMIC) > > > > due to internal use of per_cpu variables, which requires preemption > > > > disabling/enabling. > > > > > > > > reported as "BUG: "using smp_processor_id() in preemptible" by syzkaller > > > > > > > > Reported-by: syzbot+3eec59e770685e3dc879@syzkaller.appspotmail.com > > > > Signed-off-by: Du Cheng <ducheng2@gmail.com> > > > > --- > > > > changelog > > > > v1: change to GFP_KERNEL for idr_alloc_u32() but might sleep > > > > v2: revert to GFP_ATOMIC but add preemption disable/enable protection > > > > > > > > net/qrtr/qrtr.c | 6 ++++++ > > > > 1 file changed, 6 insertions(+) > > > > > > > > diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c > > > > index edb6ac17ceca..6361f169490e 100644 > > > > --- a/net/qrtr/qrtr.c > > > > +++ b/net/qrtr/qrtr.c > > > > @@ -722,17 +722,23 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port) > > > > mutex_lock(&qrtr_port_lock); > > > > if (!*port) { > > > > min_port = QRTR_MIN_EPH_SOCKET; > > > > + idr_preload(GFP_ATOMIC); > > > > rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, QRTR_MAX_EPH_SOCKET, GFP_ATOMIC); > > > > + idr_preload_end(); > > > > > > This seems "odd" to me. We are asking idr_alloc_u32() to abide by > > > GFP_ATOMIC, so why do we need to "preload" it with the same type of > > > allocation? > > > > > > Is there something in the idr/radix/xarray code that can't really handle > > > GFP_ATOMIC during a "normal" idr allocation that is causing this warning > > > to be hit? Why is this change the "correct" one? > > > > > > thanks, > > > > > > greg k-h > > > > > > >From the comment above idr_preload() in lib/radix-tree.c:1460 > > /** > > * idr_preload - preload for idr_alloc() > > * @gfp_mask: allocation mask to use for preloading > > * > > * Preallocate memory to use for the next call to idr_alloc(). This function > > * returns with preemption disabled. It will be enabled by idr_preload_end(). > > */ > > > > idr_alloc is a very simple wrapper around idr_alloc_u32(). > > > > On top of radix_tree_node_alloc() which is called by idr_alloc_u32(), there is > > this comment at line 244 in the same radix-tree.c > > /* > > * This assumes that the caller has performed appropriate preallocation, and > > * that the caller has pinned this thread of control to the current CPU. > > */ > > > > Therefore the preload/preload_end are necessary, or at least should have > > preemption disabled > > Ah, so it's disabling preemption that is the key here. Still odd, why > is GFP_ATOMIC not sufficient in a normal idr_alloc() call to keep things > from doing stuff like this? Feels like a lot of "internal knowledge" is > needed here to use this api properly... > > Matthew, is the above change really correct? No. https://lore.kernel.org/netdev/20200605112922.GB19604@bombadil.infradead.org/ https://lore.kernel.org/netdev/20200605120037.17427-1-willy@infradead.org/ https://lore.kernel.org/netdev/20200914192655.GW6583@casper.infradead.org/
On Sat, Mar 27, 2021 at 03:51:10PM +0000, Matthew Wilcox wrote: > On Sat, Mar 27, 2021 at 03:31:18PM +0100, Greg Kroah-Hartman wrote: > > On Sat, Mar 27, 2021 at 10:25:20PM +0800, Du Cheng wrote: > > > On Sat, Mar 27, 2021 at 03:12:14PM +0100, Greg Kroah-Hartman wrote: > > > > Adding the xarray maintainer... > > > > > > > > On Sat, Mar 27, 2021 at 10:07:02PM +0800, Du Cheng wrote: > > > > > add idr_preload() and idr_preload_end() around idr_alloc_u32(GFP_ATOMIC) > > > > > due to internal use of per_cpu variables, which requires preemption > > > > > disabling/enabling. > > > > > > > > > > reported as "BUG: "using smp_processor_id() in preemptible" by syzkaller > > > > > > > > > > Reported-by: syzbot+3eec59e770685e3dc879@syzkaller.appspotmail.com > > > > > Signed-off-by: Du Cheng <ducheng2@gmail.com> > > > > > --- > > > > > changelog > > > > > v1: change to GFP_KERNEL for idr_alloc_u32() but might sleep > > > > > v2: revert to GFP_ATOMIC but add preemption disable/enable protection > > > > > > > > > > net/qrtr/qrtr.c | 6 ++++++ > > > > > 1 file changed, 6 insertions(+) > > > > > > > > > > diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c > > > > > index edb6ac17ceca..6361f169490e 100644 > > > > > --- a/net/qrtr/qrtr.c > > > > > +++ b/net/qrtr/qrtr.c > > > > > @@ -722,17 +722,23 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port) > > > > > mutex_lock(&qrtr_port_lock); > > > > > if (!*port) { > > > > > min_port = QRTR_MIN_EPH_SOCKET; > > > > > + idr_preload(GFP_ATOMIC); > > > > > rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, QRTR_MAX_EPH_SOCKET, GFP_ATOMIC); > > > > > + idr_preload_end(); > > > > > > > > This seems "odd" to me. We are asking idr_alloc_u32() to abide by > > > > GFP_ATOMIC, so why do we need to "preload" it with the same type of > > > > allocation? > > > > > > > > Is there something in the idr/radix/xarray code that can't really handle > > > > GFP_ATOMIC during a "normal" idr allocation that is causing this warning > > > > to be hit? Why is this change the "correct" one? > > > > > > > > thanks, > > > > > > > > greg k-h > > > > > > > > > >From the comment above idr_preload() in lib/radix-tree.c:1460 > > > /** > > > * idr_preload - preload for idr_alloc() > > > * @gfp_mask: allocation mask to use for preloading > > > * > > > * Preallocate memory to use for the next call to idr_alloc(). This function > > > * returns with preemption disabled. It will be enabled by idr_preload_end(). > > > */ > > > > > > idr_alloc is a very simple wrapper around idr_alloc_u32(). > > > > > > On top of radix_tree_node_alloc() which is called by idr_alloc_u32(), there is > > > this comment at line 244 in the same radix-tree.c > > > /* > > > * This assumes that the caller has performed appropriate preallocation, and > > > * that the caller has pinned this thread of control to the current CPU. > > > */ > > > > > > Therefore the preload/preload_end are necessary, or at least should have > > > preemption disabled > > > > Ah, so it's disabling preemption that is the key here. Still odd, why > > is GFP_ATOMIC not sufficient in a normal idr_alloc() call to keep things > > from doing stuff like this? Feels like a lot of "internal knowledge" is > > needed here to use this api properly... > > > > Matthew, is the above change really correct? > > No. > > https://lore.kernel.org/netdev/20200605112922.GB19604@bombadil.infradead.org/ > https://lore.kernel.org/netdev/20200605120037.17427-1-willy@infradead.org/ > https://lore.kernel.org/netdev/20200914192655.GW6583@casper.infradead.org/ > Ok, it looks like this code is just abandonded, should we remove it entirely as no one wants to maintain it? thanks, greg k-h
On Sun, Mar 28, 2021 at 08:56:17AM +0200, Greg Kroah-Hartman wrote: > On Sat, Mar 27, 2021 at 03:51:10PM +0000, Matthew Wilcox wrote: > > On Sat, Mar 27, 2021 at 03:31:18PM +0100, Greg Kroah-Hartman wrote: > > > On Sat, Mar 27, 2021 at 10:25:20PM +0800, Du Cheng wrote: > > > > On Sat, Mar 27, 2021 at 03:12:14PM +0100, Greg Kroah-Hartman wrote: > > > > > Adding the xarray maintainer... > > > > > > > > > > On Sat, Mar 27, 2021 at 10:07:02PM +0800, Du Cheng wrote: > > > > > > add idr_preload() and idr_preload_end() around idr_alloc_u32(GFP_ATOMIC) > > > > > > due to internal use of per_cpu variables, which requires preemption > > > > > > disabling/enabling. > > > > > > > > > > > > reported as "BUG: "using smp_processor_id() in preemptible" by syzkaller > > > > > > > > > > > > Reported-by: syzbot+3eec59e770685e3dc879@syzkaller.appspotmail.com > > > > > > Signed-off-by: Du Cheng <ducheng2@gmail.com> > > > > > > --- > > > > > > changelog > > > > > > v1: change to GFP_KERNEL for idr_alloc_u32() but might sleep > > > > > > v2: revert to GFP_ATOMIC but add preemption disable/enable protection > > > > > > > > > > > > net/qrtr/qrtr.c | 6 ++++++ > > > > > > 1 file changed, 6 insertions(+) > > > > > > > > > > > > diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c > > > > > > index edb6ac17ceca..6361f169490e 100644 > > > > > > --- a/net/qrtr/qrtr.c > > > > > > +++ b/net/qrtr/qrtr.c > > > > > > @@ -722,17 +722,23 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port) > > > > > > mutex_lock(&qrtr_port_lock); > > > > > > if (!*port) { > > > > > > min_port = QRTR_MIN_EPH_SOCKET; > > > > > > + idr_preload(GFP_ATOMIC); > > > > > > rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, QRTR_MAX_EPH_SOCKET, GFP_ATOMIC); > > > > > > + idr_preload_end(); > > > > > > > > > > This seems "odd" to me. We are asking idr_alloc_u32() to abide by > > > > > GFP_ATOMIC, so why do we need to "preload" it with the same type of > > > > > allocation? > > > > > > > > > > Is there something in the idr/radix/xarray code that can't really handle > > > > > GFP_ATOMIC during a "normal" idr allocation that is causing this warning > > > > > to be hit? Why is this change the "correct" one? > > > > > > > > > > thanks, > > > > > > > > > > greg k-h > > > > > > > > > > > > >From the comment above idr_preload() in lib/radix-tree.c:1460 > > > > /** > > > > * idr_preload - preload for idr_alloc() > > > > * @gfp_mask: allocation mask to use for preloading > > > > * > > > > * Preallocate memory to use for the next call to idr_alloc(). This function > > > > * returns with preemption disabled. It will be enabled by idr_preload_end(). > > > > */ > > > > > > > > idr_alloc is a very simple wrapper around idr_alloc_u32(). > > > > > > > > On top of radix_tree_node_alloc() which is called by idr_alloc_u32(), there is > > > > this comment at line 244 in the same radix-tree.c > > > > /* > > > > * This assumes that the caller has performed appropriate preallocation, and > > > > * that the caller has pinned this thread of control to the current CPU. > > > > */ > > > > > > > > Therefore the preload/preload_end are necessary, or at least should have > > > > preemption disabled > > > > > > Ah, so it's disabling preemption that is the key here. Still odd, why > > > is GFP_ATOMIC not sufficient in a normal idr_alloc() call to keep things > > > from doing stuff like this? Feels like a lot of "internal knowledge" is > > > needed here to use this api properly... > > > > > > Matthew, is the above change really correct? > > > > No. > > > > https://lore.kernel.org/netdev/20200605112922.GB19604@bombadil.infradead.org/ > > https://lore.kernel.org/netdev/20200605120037.17427-1-willy@infradead.org/ > > https://lore.kernel.org/netdev/20200914192655.GW6583@casper.infradead.org/ > > > > Ok, it looks like this code is just abandonded, should we remove it > entirely as no one wants to maintain it? Fine by me. I don't use it. Better to get rid of abandonware than keep a potential source of security holes.
On Sun, Mar 28, 2021 at 11:04:17AM +0100, Matthew Wilcox wrote: > On Sun, Mar 28, 2021 at 08:56:17AM +0200, Greg Kroah-Hartman wrote: > > On Sat, Mar 27, 2021 at 03:51:10PM +0000, Matthew Wilcox wrote: > > > On Sat, Mar 27, 2021 at 03:31:18PM +0100, Greg Kroah-Hartman wrote: > > > > On Sat, Mar 27, 2021 at 10:25:20PM +0800, Du Cheng wrote: > > > > > On Sat, Mar 27, 2021 at 03:12:14PM +0100, Greg Kroah-Hartman wrote: > > > > > > Adding the xarray maintainer... > > > > > > > > > > > > On Sat, Mar 27, 2021 at 10:07:02PM +0800, Du Cheng wrote: > > > > > > > add idr_preload() and idr_preload_end() around idr_alloc_u32(GFP_ATOMIC) > > > > > > > due to internal use of per_cpu variables, which requires preemption > > > > > > > disabling/enabling. > > > > > > > > > > > > > > reported as "BUG: "using smp_processor_id() in preemptible" by syzkaller > > > > > > > > > > > > > > Reported-by: syzbot+3eec59e770685e3dc879@syzkaller.appspotmail.com > > > > > > > Signed-off-by: Du Cheng <ducheng2@gmail.com> > > > > > > > --- > > > > > > > changelog > > > > > > > v1: change to GFP_KERNEL for idr_alloc_u32() but might sleep > > > > > > > v2: revert to GFP_ATOMIC but add preemption disable/enable protection > > > > > > > > > > > > > > net/qrtr/qrtr.c | 6 ++++++ > > > > > > > 1 file changed, 6 insertions(+) > > > > > > > > > > > > > > diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c > > > > > > > index edb6ac17ceca..6361f169490e 100644 > > > > > > > --- a/net/qrtr/qrtr.c > > > > > > > +++ b/net/qrtr/qrtr.c > > > > > > > @@ -722,17 +722,23 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port) > > > > > > > mutex_lock(&qrtr_port_lock); > > > > > > > if (!*port) { > > > > > > > min_port = QRTR_MIN_EPH_SOCKET; > > > > > > > + idr_preload(GFP_ATOMIC); > > > > > > > rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, QRTR_MAX_EPH_SOCKET, GFP_ATOMIC); > > > > > > > + idr_preload_end(); > > > > > > > > > > > > This seems "odd" to me. We are asking idr_alloc_u32() to abide by > > > > > > GFP_ATOMIC, so why do we need to "preload" it with the same type of > > > > > > allocation? > > > > > > > > > > > > Is there something in the idr/radix/xarray code that can't really handle > > > > > > GFP_ATOMIC during a "normal" idr allocation that is causing this warning > > > > > > to be hit? Why is this change the "correct" one? > > > > > > > > > > > > thanks, > > > > > > > > > > > > greg k-h > > > > > > > > > > > > > > > >From the comment above idr_preload() in lib/radix-tree.c:1460 > > > > > /** > > > > > * idr_preload - preload for idr_alloc() > > > > > * @gfp_mask: allocation mask to use for preloading > > > > > * > > > > > * Preallocate memory to use for the next call to idr_alloc(). This function > > > > > * returns with preemption disabled. It will be enabled by idr_preload_end(). > > > > > */ > > > > > > > > > > idr_alloc is a very simple wrapper around idr_alloc_u32(). > > > > > > > > > > On top of radix_tree_node_alloc() which is called by idr_alloc_u32(), there is > > > > > this comment at line 244 in the same radix-tree.c > > > > > /* > > > > > * This assumes that the caller has performed appropriate preallocation, and > > > > > * that the caller has pinned this thread of control to the current CPU. > > > > > */ > > > > > > > > > > Therefore the preload/preload_end are necessary, or at least should have > > > > > preemption disabled > > > > > > > > Ah, so it's disabling preemption that is the key here. Still odd, why > > > > is GFP_ATOMIC not sufficient in a normal idr_alloc() call to keep things > > > > from doing stuff like this? Feels like a lot of "internal knowledge" is > > > > needed here to use this api properly... > > > > > > > > Matthew, is the above change really correct? > > > > > > No. > > > > > > https://lore.kernel.org/netdev/20200605112922.GB19604@bombadil.infradead.org/ > > > https://lore.kernel.org/netdev/20200605120037.17427-1-willy@infradead.org/ > > > https://lore.kernel.org/netdev/20200914192655.GW6583@casper.infradead.org/ > > > > > > > Ok, it looks like this code is just abandonded, should we remove it > > entirely as no one wants to maintain it? > > Fine by me. I don't use it. Better to get rid of abandonware than keep > a potential source of security holes. Hi Manivannan, For your information. Regards, Du Cheng
On Mon, Mar 29, 2021 at 06:55:56PM +0800, Du Cheng wrote: > On Sun, Mar 28, 2021 at 11:04:17AM +0100, Matthew Wilcox wrote: > > On Sun, Mar 28, 2021 at 08:56:17AM +0200, Greg Kroah-Hartman wrote: > > > On Sat, Mar 27, 2021 at 03:51:10PM +0000, Matthew Wilcox wrote: > > > > On Sat, Mar 27, 2021 at 03:31:18PM +0100, Greg Kroah-Hartman wrote: > > > > > On Sat, Mar 27, 2021 at 10:25:20PM +0800, Du Cheng wrote: > > > > > > On Sat, Mar 27, 2021 at 03:12:14PM +0100, Greg Kroah-Hartman wrote: > > > > > > > Adding the xarray maintainer... > > > > > > > > > > > > > > On Sat, Mar 27, 2021 at 10:07:02PM +0800, Du Cheng wrote: > > > > > > > > add idr_preload() and idr_preload_end() around idr_alloc_u32(GFP_ATOMIC) > > > > > > > > due to internal use of per_cpu variables, which requires preemption > > > > > > > > disabling/enabling. > > > > > > > > > > > > > > > > reported as "BUG: "using smp_processor_id() in preemptible" by syzkaller > > > > > > > > > > > > > > > > Reported-by: syzbot+3eec59e770685e3dc879@syzkaller.appspotmail.com > > > > > > > > Signed-off-by: Du Cheng <ducheng2@gmail.com> > > > > > > > > --- > > > > > > > > changelog > > > > > > > > v1: change to GFP_KERNEL for idr_alloc_u32() but might sleep > > > > > > > > v2: revert to GFP_ATOMIC but add preemption disable/enable protection > > > > > > > > > > > > > > > > net/qrtr/qrtr.c | 6 ++++++ > > > > > > > > 1 file changed, 6 insertions(+) > > > > > > > > > > > > > > > > diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c > > > > > > > > index edb6ac17ceca..6361f169490e 100644 > > > > > > > > --- a/net/qrtr/qrtr.c > > > > > > > > +++ b/net/qrtr/qrtr.c > > > > > > > > @@ -722,17 +722,23 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port) > > > > > > > > mutex_lock(&qrtr_port_lock); > > > > > > > > if (!*port) { > > > > > > > > min_port = QRTR_MIN_EPH_SOCKET; > > > > > > > > + idr_preload(GFP_ATOMIC); > > > > > > > > rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, QRTR_MAX_EPH_SOCKET, GFP_ATOMIC); > > > > > > > > + idr_preload_end(); > > > > > > > [...] > > > Ok, it looks like this code is just abandonded, should we remove it > > > entirely as no one wants to maintain it? > > > > Fine by me. I don't use it. Better to get rid of abandonware than keep > > a potential source of security holes. > > Hi Manivannan, > > For your information. > Thanks for letting me know. I'll look into it once back to work. Thanks, Mani > Regards, > Du Cheng
diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c index edb6ac17ceca..6361f169490e 100644 --- a/net/qrtr/qrtr.c +++ b/net/qrtr/qrtr.c @@ -722,17 +722,23 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port) mutex_lock(&qrtr_port_lock); if (!*port) { min_port = QRTR_MIN_EPH_SOCKET; + idr_preload(GFP_ATOMIC); rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, QRTR_MAX_EPH_SOCKET, GFP_ATOMIC); + idr_preload_end(); if (!rc) *port = min_port; } else if (*port < QRTR_MIN_EPH_SOCKET && !capable(CAP_NET_ADMIN)) { rc = -EACCES; } else if (*port == QRTR_PORT_CTRL) { min_port = 0; + idr_preload(GFP_ATOMIC); rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, 0, GFP_ATOMIC); + idr_preload_end(); } else { min_port = *port; + idr_preload(GFP_ATOMIC); rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, *port, GFP_ATOMIC); + idr_preload_end(); if (!rc) *port = min_port; }
add idr_preload() and idr_preload_end() around idr_alloc_u32(GFP_ATOMIC) due to internal use of per_cpu variables, which requires preemption disabling/enabling. reported as "BUG: "using smp_processor_id() in preemptible" by syzkaller Reported-by: syzbot+3eec59e770685e3dc879@syzkaller.appspotmail.com Signed-off-by: Du Cheng <ducheng2@gmail.com> --- changelog v1: change to GFP_KERNEL for idr_alloc_u32() but might sleep v2: revert to GFP_ATOMIC but add preemption disable/enable protection net/qrtr/qrtr.c | 6 ++++++ 1 file changed, 6 insertions(+)