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authorEric Dumazet <edumazet@google.com>2012-06-12 15:24:40 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-07-16 09:04:42 -0700
commit2c07f25ea7800adb36cd8da9b58c4ecd3fc3d064 (patch)
treeb312e3b679b544de20569f8e31dd1469e8a72be1 /fs/splice.c
parent5318edefb61eddf91d4c4a089644fcee3ccfda62 (diff)
splice: fix racy pipe->buffers uses
commit 047fe3605235888f3ebcda0c728cb31937eadfe6 upstream. Dave Jones reported a kernel BUG at mm/slub.c:3474! triggered by splice_shrink_spd() called from vmsplice_to_pipe() commit 35f3d14dbbc5 (pipe: add support for shrinking and growing pipes) added capability to adjust pipe->buffers. Problem is some paths don't hold pipe mutex and assume pipe->buffers doesn't change for their duration. Fix this by adding nr_pages_max field in struct splice_pipe_desc, and use it in place of pipe->buffers where appropriate. splice_shrink_spd() loses its struct pipe_inode_info argument. Reported-by: Dave Jones <davej@redhat.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Tom Herbert <therbert@google.com> Tested-by: Dave Jones <davej@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> [bwh: Backported to 3.2: - Adjust context in vmsplice_to_pipe() - Update one more call to splice_shrink_spd(), from skb_splice_bits()] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/splice.c')
-rw-r--r--fs/splice.c35
1 files changed, 20 insertions, 15 deletions
diff --git a/fs/splice.c b/fs/splice.c
index f8476841eb0..5cac690f810 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -273,13 +273,16 @@ void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
* Check if we need to grow the arrays holding pages and partial page
* descriptions.
*/
-int splice_grow_spd(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
+int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
{
- if (pipe->buffers <= PIPE_DEF_BUFFERS)
+ unsigned int buffers = ACCESS_ONCE(pipe->buffers);
+
+ spd->nr_pages_max = buffers;
+ if (buffers <= PIPE_DEF_BUFFERS)
return 0;
- spd->pages = kmalloc(pipe->buffers * sizeof(struct page *), GFP_KERNEL);
- spd->partial = kmalloc(pipe->buffers * sizeof(struct partial_page), GFP_KERNEL);
+ spd->pages = kmalloc(buffers * sizeof(struct page *), GFP_KERNEL);
+ spd->partial = kmalloc(buffers * sizeof(struct partial_page), GFP_KERNEL);
if (spd->pages && spd->partial)
return 0;
@@ -289,10 +292,9 @@ int splice_grow_spd(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
return -ENOMEM;
}
-void splice_shrink_spd(struct pipe_inode_info *pipe,
- struct splice_pipe_desc *spd)
+void splice_shrink_spd(struct splice_pipe_desc *spd)
{
- if (pipe->buffers <= PIPE_DEF_BUFFERS)
+ if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
return;
kfree(spd->pages);
@@ -315,6 +317,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
+ .nr_pages_max = PIPE_DEF_BUFFERS,
.flags = flags,
.ops = &page_cache_pipe_buf_ops,
.spd_release = spd_release_page,
@@ -326,7 +329,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
index = *ppos >> PAGE_CACHE_SHIFT;
loff = *ppos & ~PAGE_CACHE_MASK;
req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
- nr_pages = min(req_pages, pipe->buffers);
+ nr_pages = min(req_pages, spd.nr_pages_max);
/*
* Lookup the (hopefully) full range of pages we need.
@@ -497,7 +500,7 @@ fill_it:
if (spd.nr_pages)
error = splice_to_pipe(pipe, &spd);
- splice_shrink_spd(pipe, &spd);
+ splice_shrink_spd(&spd);
return error;
}
@@ -598,6 +601,7 @@ ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
+ .nr_pages_max = PIPE_DEF_BUFFERS,
.flags = flags,
.ops = &default_pipe_buf_ops,
.spd_release = spd_release_page,
@@ -608,8 +612,8 @@ ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
res = -ENOMEM;
vec = __vec;
- if (pipe->buffers > PIPE_DEF_BUFFERS) {
- vec = kmalloc(pipe->buffers * sizeof(struct iovec), GFP_KERNEL);
+ if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
+ vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
if (!vec)
goto shrink_ret;
}
@@ -617,7 +621,7 @@ ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
offset = *ppos & ~PAGE_CACHE_MASK;
nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
- for (i = 0; i < nr_pages && i < pipe->buffers && len; i++) {
+ for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
struct page *page;
page = alloc_page(GFP_USER);
@@ -665,7 +669,7 @@ ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
shrink_ret:
if (vec != __vec)
kfree(vec);
- splice_shrink_spd(pipe, &spd);
+ splice_shrink_spd(&spd);
return res;
err:
@@ -1612,6 +1616,7 @@ static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
+ .nr_pages_max = PIPE_DEF_BUFFERS,
.flags = flags,
.ops = &user_page_pipe_buf_ops,
.spd_release = spd_release_page,
@@ -1627,13 +1632,13 @@ static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
spd.partial, flags & SPLICE_F_GIFT,
- pipe->buffers);
+ spd.nr_pages_max);
if (spd.nr_pages <= 0)
ret = spd.nr_pages;
else
ret = splice_to_pipe(pipe, &spd);
- splice_shrink_spd(pipe, &spd);
+ splice_shrink_spd(&spd);
return ret;
}