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.
Cc: Dmitry Safonov <0x7f454c46@xxxxxxxxx>
Signed-off-by: Andrei Vagin <avagin@xxxxxxxxx>
---
fs/pipe.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/fs/pipe.c b/fs/pipe.c
index 6d4342bad9f1..45565773ec33 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -802,7 +802,7 @@ 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) {
@@ -845,7 +845,7 @@ void free_pipe_info(struct pipe_inode_info *pipe)
}
if (pipe->tmp_page)
__free_page(pipe->tmp_page);
- kfree(pipe->bufs);
+ kvfree(pipe->bufs);
kfree(pipe);
}
@@ -1260,8 +1260,7 @@ 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;
@@ -1288,7 +1287,7 @@ 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)
--
2.33.1
