diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-04-14 15:09:40 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-04-14 15:09:40 -0700 |
commit | 6b3a707736301c2128ca85ce85fb13f60b5e350a (patch) | |
tree | 2bf1892cf29121150adece8d1221ecd513a4e792 /fs/pipe.c | |
parent | 4443f8e6ac7755cd775c70d08be8042dc2f936cb (diff) | |
parent | 15fab63e1e57be9fdb5eec1bbc5916e9825e9acb (diff) | |
download | linux-stable-6b3a707736301c2128ca85ce85fb13f60b5e350a.tar.gz linux-stable-6b3a707736301c2128ca85ce85fb13f60b5e350a.tar.bz2 linux-stable-6b3a707736301c2128ca85ce85fb13f60b5e350a.zip |
Merge branch 'page-refs' (page ref overflow)
Merge page ref overflow branch.
Jann Horn reported that he can overflow the page ref count with
sufficient memory (and a filesystem that is intentionally extremely
slow).
Admittedly it's not exactly easy. To have more than four billion
references to a page requires a minimum of 32GB of kernel memory just
for the pointers to the pages, much less any metadata to keep track of
those pointers. Jann needed a total of 140GB of memory and a specially
crafted filesystem that leaves all reads pending (in order to not ever
free the page references and just keep adding more).
Still, we have a fairly straightforward way to limit the two obvious
user-controllable sources of page references: direct-IO like page
references gotten through get_user_pages(), and the splice pipe page
duplication. So let's just do that.
* branch page-refs:
fs: prevent page refcount overflow in pipe_buf_get
mm: prevent get_user_pages() from overflowing page refcount
mm: add 'try_get_page()' helper function
mm: make page ref count overflow check tighter and more explicit
Diffstat (limited to 'fs/pipe.c')
-rw-r--r-- | fs/pipe.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/pipe.c b/fs/pipe.c index 070aad543382..41065901106b 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -188,9 +188,9 @@ EXPORT_SYMBOL(generic_pipe_buf_steal); * in the tee() system call, when we duplicate the buffers in one * pipe into another. */ -void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf) +bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { - get_page(buf->page); + return try_get_page(buf->page); } EXPORT_SYMBOL(generic_pipe_buf_get); |