fs/pipe: use kvcalloc to allocate a pipe_buffer array

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>

diff --git a/fs/pipe.c b/fs/pipe.c
index 2667db9506e2f2853f46e551332562dec10618af..ba0841b6674b1c2405554990d2de3cb826a3ee4d 100644 (file)
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -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)