2021-07-27 05:35:54

by Vasily Averin

Subject: [PATCH v7 02/10] memcg: enable accounting for pollfd and select bits arrays

User can call select/poll system calls with a large number of assigned
file descriptors and force kernel to allocate up to several pages of memory
till end of these sleeping system calls. We have here long-living
unaccounted per-task allocations.

It makes sense to account for these allocations to restrict the host's
memory consumption from inside the memcg-limited container.

Signed-off-by: Vasily Averin <[email protected]>
---
fs/select.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/select.c b/fs/select.c
index 945896d..e83e563 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -655,7 +655,7 @@ int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
goto out_nofds;

alloc_size = 6 * size;
- bits = kvmalloc(alloc_size, GFP_KERNEL);
+ bits = kvmalloc(alloc_size, GFP_KERNEL_ACCOUNT);
if (!bits)
goto out_nofds;
}
@@ -1000,7 +1000,7 @@ static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,

len = min(todo, POLLFD_PER_PAGE);
walk = walk->next = kmalloc(struct_size(walk, entries, len),
- GFP_KERNEL);
+ GFP_KERNEL_ACCOUNT);
if (!walk) {
err = -ENOMEM;
goto out_fds;
--
1.8.3.1

2021-07-27 21:42:34

by Shakeel Butt

Subject: Re: [PATCH v7 02/10] memcg: enable accounting for pollfd and select bits arrays

On Mon, Jul 26, 2021 at 10:33 PM Vasily Averin <[email protected]> wrote:
>
> User can call select/poll system calls with a large number of assigned
> file descriptors and force kernel to allocate up to several pages of memory
> till end of these sleeping system calls. We have here long-living
> unaccounted per-task allocations.
>
> It makes sense to account for these allocations to restrict the host's
> memory consumption from inside the memcg-limited container.
>
> Signed-off-by: Vasily Averin <[email protected]>
> ---
> fs/select.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/select.c b/fs/select.c
> index 945896d..e83e563 100644
> --- a/fs/select.c
> +++ b/fs/select.c
> @@ -655,7 +655,7 @@ int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
> goto out_nofds;
>
> alloc_size = 6 * size;
> - bits = kvmalloc(alloc_size, GFP_KERNEL);
> + bits = kvmalloc(alloc_size, GFP_KERNEL_ACCOUNT);

What about the similar allocation in compat_core_sys_select()? Also
what about the allocation in poll_get_entry()?

> if (!bits)
> goto out_nofds;
> }
> @@ -1000,7 +1000,7 @@ static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
>
> len = min(todo, POLLFD_PER_PAGE);
> walk = walk->next = kmalloc(struct_size(walk, entries, len),
> - GFP_KERNEL);
> + GFP_KERNEL_ACCOUNT);
> if (!walk) {
> err = -ENOMEM;
> goto out_fds;
> --
> 1.8.3.1
>