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fs/pipe: use kvcalloc to allocate a pipe_buffer array

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Right now, kcalloc is used to allocate a pipe_buffer array.  The size of
the pipe_buffer struct is 40 bytes.  kcalloc allows allocating reliably
chunks with sizes less or equal to PAGE_ALLOC_COSTLY_ORDER (3).  It
means that the maximum pipe size is 3.2MB in this case.

In CRIU, we use pipes to dump processes memory.  CRIU freezes a target
process, injects a parasite code into it and then this code splices
memory into pipes.  If a maximum pipe size is small, we need to do many
iterations or create many pipes.

kvcalloc attempt to allocate physically contiguous memory, but upon
failure, fall back to non-contiguous (vmalloc) allocation and so it
isn't limited by PAGE_ALLOC_COSTLY_ORDER.

The maximum pipe size for non-root users is limited by the
/proc/sys/fs/pipe-max-size sysctl that is 1MB by default, so only the
root user will be able to trigger vmalloc allocations.

Link: https://lkml.kernel.org/r/20220104171058.22580-1-avagin@gmail.com
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrei Vagin 2022-03-23 16:06:17 -07:00 committed by Linus Torvalds
parent f9a40b0890
commit 5a519c8fe4
1 changed files with 4 additions and 5 deletions
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9
fs/pipe.c
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@ -804,7 +804,7 @@ struct pipe_inode_info *alloc_pipe_info(void)
if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
goto out_revert_acct;
pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
pipe->bufs = kvcalloc(pipe_bufs, sizeof(struct pipe_buffer),
GFP_KERNEL_ACCOUNT);
if (pipe->bufs) {
@ -849,7 +849,7 @@ void free_pipe_info(struct pipe_inode_info *pipe)
#endif
if (pipe->tmp_page)
__free_page(pipe->tmp_page);
kfree(pipe->bufs);
kvfree(pipe->bufs);
kfree(pipe);
}
@ -1264,8 +1264,7 @@ int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
if (nr_slots < n)
return -EBUSY;
bufs = kcalloc(nr_slots, sizeof(*bufs),
GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
bufs = kvcalloc(nr_slots, sizeof(*bufs), GFP_KERNEL_ACCOUNT);
if (unlikely(!bufs))
return -ENOMEM;
@ -1292,7 +1291,7 @@ int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
head = n;
tail = 0;
kfree(pipe->bufs);
kvfree(pipe->bufs);
pipe->bufs = bufs;
pipe->ring_size = nr_slots;
if (pipe->max_usage > nr_slots)