[PATCH rdma-next] RDMA/core: Silence oversized kvmalloc() warning

[PATCH rdma-next] RDMA/core: Silence oversized kvmalloc() warning

[Leon Romanovsky]

From: Shay Drory <shayd@nvidia.com>

syzkaller triggered an oversized kvmalloc() warning.
Silence it by adding __GFP_NOWARN.

syzkaller log:
 WARNING: CPU: 7 PID: 518 at mm/util.c:665 __kvmalloc_node_noprof+0x175/0x180
 CPU: 7 UID: 0 PID: 518 Comm: c_repro Not tainted 6.11.0-rc6+ #6
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 RIP: 0010:__kvmalloc_node_noprof+0x175/0x180
 RSP: 0018:ffffc90001e67c10 EFLAGS: 00010246
 RAX: 0000000000000100 RBX: 0000000000000400 RCX: ffffffff8149d46b
 RDX: 0000000000000000 RSI: ffff8881030fae80 RDI: 0000000000000002
 RBP: 000000712c800000 R08: 0000000000000100 R09: 0000000000000000
 R10: ffffc90001e67c10 R11: 0030ae0601000000 R12: 0000000000000000
 R13: 0000000000000000 R14: 00000000ffffffff R15: 0000000000000000
 FS:  00007fde79159740(0000) GS:ffff88813bdc0000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000020000180 CR3: 0000000105eb4005 CR4: 00000000003706b0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Call Trace:
  <TASK>
  ib_umem_odp_get+0x1f6/0x390
  mlx5_ib_reg_user_mr+0x1e8/0x450
  ib_uverbs_reg_mr+0x28b/0x440
  ib_uverbs_write+0x7d3/0xa30
  vfs_write+0x1ac/0x6c0
  ksys_write+0x134/0x170
  ? __sanitizer_cov_trace_pc+0x1c/0x50
  do_syscall_64+0x50/0x110
  entry_SYSCALL_64_after_hwframe+0x76/0x7e

Fixes: 37824952dc8f ("RDMA/odp: Use kvcalloc for the dma_list and page_list")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/infiniband/core/umem_odp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
index e9fa22d31c23..c48ef6083020 100644
--- a/drivers/infiniband/core/umem_odp.c
+++ b/drivers/infiniband/core/umem_odp.c
@@ -76,12 +76,14 @@ static inline int ib_init_umem_odp(struct ib_umem_odp *umem_odp,
 
 		npfns = (end - start) >> PAGE_SHIFT;
 		umem_odp->pfn_list = kvcalloc(
-			npfns, sizeof(*umem_odp->pfn_list), GFP_KERNEL);
+			npfns, sizeof(*umem_odp->pfn_list),
+			GFP_KERNEL | __GFP_NOWARN);
 		if (!umem_odp->pfn_list)
 			return -ENOMEM;
 
 		umem_odp->dma_list = kvcalloc(
-			ndmas, sizeof(*umem_odp->dma_list), GFP_KERNEL);
+			ndmas, sizeof(*umem_odp->dma_list),
+			GFP_KERNEL | __GFP_NOWARN);
 		if (!umem_odp->dma_list) {
 			ret = -ENOMEM;
 			goto out_pfn_list;
-- 
2.48.1

Re: [PATCH rdma-next] RDMA/core: Silence oversized kvmalloc() warning

[Jason Gunthorpe]

On Wed, Mar 19, 2025 at 02:42:21PM +0200, Leon Romanovsky wrote:
> From: Shay Drory <shayd@nvidia.com>
> 
> syzkaller triggered an oversized kvmalloc() warning.
> Silence it by adding __GFP_NOWARN.

I don't think GFP_NOWARN is the right thing..

We've hit this before and I think we ended up adding a size limit
check prior to the kvmalloc to prevent the overflow triggered warning.

Jason

Re: [PATCH rdma-next] RDMA/core: Silence oversized kvmalloc() warning

[Leon Romanovsky]

On Wed, Mar 19, 2025 at 02:23:49PM -0300, Jason Gunthorpe wrote:
> On Wed, Mar 19, 2025 at 02:42:21PM +0200, Leon Romanovsky wrote:
> > From: Shay Drory <shayd@nvidia.com>
> > 
> > syzkaller triggered an oversized kvmalloc() warning.
> > Silence it by adding __GFP_NOWARN.
> 
> I don't think GFP_NOWARN is the right thing..
> 
> We've hit this before and I think we ended up adding a size limit
> check prior to the kvmalloc to prevent the overflow triggered warning.

The size check was needed before this commit was merged:
0708a0afe291 ("mm: Consider __GFP_NOWARN flag for oversized kvmalloc() calls")

From that point, the correct solution is simply provide __GFP_NOWARN flag.

Thanks

> 
> Jason
> 

Re: [PATCH rdma-next] RDMA/core: Silence oversized kvmalloc() warning

[Jason Gunthorpe]

On Wed, Mar 26, 2025 at 12:58:54PM +0200, Leon Romanovsky wrote:
> On Wed, Mar 19, 2025 at 02:23:49PM -0300, Jason Gunthorpe wrote:
> > On Wed, Mar 19, 2025 at 02:42:21PM +0200, Leon Romanovsky wrote:
> > > From: Shay Drory <shayd@nvidia.com>
> > > 
> > > syzkaller triggered an oversized kvmalloc() warning.
> > > Silence it by adding __GFP_NOWARN.
> > 
> > I don't think GFP_NOWARN is the right thing..
> > 
> > We've hit this before and I think we ended up adding a size limit
> > check prior to the kvmalloc to prevent the overflow triggered warning.
> 
> The size check was needed before this commit was merged:
> 0708a0afe291 ("mm: Consider __GFP_NOWARN flag for oversized kvmalloc() calls")
> 
> From that point, the correct solution is simply provide __GFP_NOWARN flag.

I'm not sure, NOWARN removes all warnings, even normal OOM warnings
from regually sized allocations which we don't want to remove.

Jason

Re: [PATCH rdma-next] RDMA/core: Silence oversized kvmalloc() warning

[Leon Romanovsky]

On Mon, Mar 31, 2025, at 20:45, Jason Gunthorpe wrote:
> On Wed, Mar 26, 2025 at 12:58:54PM +0200, Leon Romanovsky wrote:
>> On Wed, Mar 19, 2025 at 02:23:49PM -0300, Jason Gunthorpe wrote:
>> > On Wed, Mar 19, 2025 at 02:42:21PM +0200, Leon Romanovsky wrote:
>> > > From: Shay Drory <shayd@nvidia.com>
>> > > 
>> > > syzkaller triggered an oversized kvmalloc() warning.
>> > > Silence it by adding __GFP_NOWARN.
>> > 
>> > I don't think GFP_NOWARN is the right thing..
>> > 
>> > We've hit this before and I think we ended up adding a size limit
>> > check prior to the kvmalloc to prevent the overflow triggered warning.
>> 
>> The size check was needed before this commit was merged:
>> 0708a0afe291 ("mm: Consider __GFP_NOWARN flag for oversized kvmalloc() calls")
>> 
>> From that point, the correct solution is simply provide __GFP_NOWARN flag.
>
> I'm not sure, NOWARN removes all warnings, even normal OOM warnings
> from regually sized allocations which we don't want to remove.

I disagree, this allocation is called from user space. We can safely skip OOM messages and error here will be enough.

Thanks 

>
> Jason

Re: [PATCH rdma-next] RDMA/core: Silence oversized kvmalloc() warning

[Jason Gunthorpe]

On Mon, Mar 31, 2025 at 10:04:05PM +0300, Leon Romanovsky wrote:
> 
> 
> On Mon, Mar 31, 2025, at 20:45, Jason Gunthorpe wrote:
> > On Wed, Mar 26, 2025 at 12:58:54PM +0200, Leon Romanovsky wrote:
> >> On Wed, Mar 19, 2025 at 02:23:49PM -0300, Jason Gunthorpe wrote:
> >> > On Wed, Mar 19, 2025 at 02:42:21PM +0200, Leon Romanovsky wrote:
> >> > > From: Shay Drory <shayd@nvidia.com>
> >> > > 
> >> > > syzkaller triggered an oversized kvmalloc() warning.
> >> > > Silence it by adding __GFP_NOWARN.
> >> > 
> >> > I don't think GFP_NOWARN is the right thing..
> >> > 
> >> > We've hit this before and I think we ended up adding a size limit
> >> > check prior to the kvmalloc to prevent the overflow triggered warning.
> >> 
> >> The size check was needed before this commit was merged:
> >> 0708a0afe291 ("mm: Consider __GFP_NOWARN flag for oversized kvmalloc() calls")
> >> 
> >> From that point, the correct solution is simply provide __GFP_NOWARN flag.
> >
> > I'm not sure, NOWARN removes all warnings, even normal OOM warnings
> > from regually sized allocations which we don't want to remove.
> 
> I disagree, this allocation is called from user space. We can safely
> skip OOM messages and error here will be enough.

That is not the standard, we OOM splat on all userspace allocations
too.

GFP_NOWARN is supposed to be used in cases where the OOM has a
recovery and nothing will fail.

I think the right thing here is to limit the size, though I'm not
really sure what the limit should be.

Jason

Re: [PATCH rdma-next] RDMA/core: Silence oversized kvmalloc() warning

[Leon Romanovsky]

On Tue, Apr 01, 2025 at 01:35:04PM -0300, Jason Gunthorpe wrote:
> On Mon, Mar 31, 2025 at 10:04:05PM +0300, Leon Romanovsky wrote:
> > 
> > 
> > On Mon, Mar 31, 2025, at 20:45, Jason Gunthorpe wrote:
> > > On Wed, Mar 26, 2025 at 12:58:54PM +0200, Leon Romanovsky wrote:
> > >> On Wed, Mar 19, 2025 at 02:23:49PM -0300, Jason Gunthorpe wrote:
> > >> > On Wed, Mar 19, 2025 at 02:42:21PM +0200, Leon Romanovsky wrote:
> > >> > > From: Shay Drory <shayd@nvidia.com>
> > >> > > 
> > >> > > syzkaller triggered an oversized kvmalloc() warning.
> > >> > > Silence it by adding __GFP_NOWARN.
> > >> > 
> > >> > I don't think GFP_NOWARN is the right thing..
> > >> > 
> > >> > We've hit this before and I think we ended up adding a size limit
> > >> > check prior to the kvmalloc to prevent the overflow triggered warning.
> > >> 
> > >> The size check was needed before this commit was merged:
> > >> 0708a0afe291 ("mm: Consider __GFP_NOWARN flag for oversized kvmalloc() calls")
> > >> 
> > >> From that point, the correct solution is simply provide __GFP_NOWARN flag.
> > >
> > > I'm not sure, NOWARN removes all warnings, even normal OOM warnings
> > > from regually sized allocations which we don't want to remove.
> > 
> > I disagree, this allocation is called from user space. We can safely
> > skip OOM messages and error here will be enough.
> 
> That is not the standard, we OOM splat on all userspace allocations
> too.
> 
> GFP_NOWARN is supposed to be used in cases where the OOM has a
> recovery and nothing will fail.

NULL returned back to the user is best way to recover.

> 
> I think the right thing here is to limit the size, though I'm not
> really sure what the limit should be.

And I still think that NOWARN is the best solution here.

Thanks

> 
> Jason

Re: [PATCH rdma-next] RDMA/core: Silence oversized kvmalloc() warning

[Leon Romanovsky]

On Wed, 19 Mar 2025 14:42:21 +0200, Leon Romanovsky wrote:
> syzkaller triggered an oversized kvmalloc() warning.
> Silence it by adding __GFP_NOWARN.
> 
> syzkaller log:
>  WARNING: CPU: 7 PID: 518 at mm/util.c:665 __kvmalloc_node_noprof+0x175/0x180
>  CPU: 7 UID: 0 PID: 518 Comm: c_repro Not tainted 6.11.0-rc6+ #6
>  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
>  RIP: 0010:__kvmalloc_node_noprof+0x175/0x180
>  RSP: 0018:ffffc90001e67c10 EFLAGS: 00010246
>  RAX: 0000000000000100 RBX: 0000000000000400 RCX: ffffffff8149d46b
>  RDX: 0000000000000000 RSI: ffff8881030fae80 RDI: 0000000000000002
>  RBP: 000000712c800000 R08: 0000000000000100 R09: 0000000000000000
>  R10: ffffc90001e67c10 R11: 0030ae0601000000 R12: 0000000000000000
>  R13: 0000000000000000 R14: 00000000ffffffff R15: 0000000000000000
>  FS:  00007fde79159740(0000) GS:ffff88813bdc0000(0000) knlGS:0000000000000000
>  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>  CR2: 0000000020000180 CR3: 0000000105eb4005 CR4: 00000000003706b0
>  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>  Call Trace:
>   <TASK>
>   ib_umem_odp_get+0x1f6/0x390
>   mlx5_ib_reg_user_mr+0x1e8/0x450
>   ib_uverbs_reg_mr+0x28b/0x440
>   ib_uverbs_write+0x7d3/0xa30
>   vfs_write+0x1ac/0x6c0
>   ksys_write+0x134/0x170
>   ? __sanitizer_cov_trace_pc+0x1c/0x50
>   do_syscall_64+0x50/0x110
>   entry_SYSCALL_64_after_hwframe+0x76/0x7e
> 
> [...]

Applied, thanks!

[1/1] RDMA/core: Silence oversized kvmalloc() warning
      https://git.kernel.org/rdma/rdma/c/9a0e6f15029e1a

Best regards,
-- 
Leon Romanovsky <leon@kernel.org>