From 047fe3605235888f3ebcda0c728cb31937eadfe6 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 12 Jun 2012 15:24:40 +0200 Subject: [PATCH] splice: fix racy pipe->buffers uses 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 Signed-off-by: Eric Dumazet Cc: Jens Axboe Cc: Alexander Viro Cc: Tom Herbert Cc: stable # 2.6.35 Tested-by: Dave Jones Signed-off-by: Jens Axboe --- fs/splice.c | 35 ++++++++++++++++++++--------------- include/linux/splice.h | 8 ++++---- kernel/relay.c | 5 +++-- kernel/trace/trace.c | 6 ++++-- mm/shmem.c | 3 ++- net/core/skbuff.c | 1 + 6 files changed, 34 insertions(+), 24 deletions(-) diff --git a/fs/splice.c b/fs/splice.c index c9f1318a3b8..7bf08fa22ec 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: @@ -1614,6 +1618,7 @@ 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, @@ -1629,13 +1634,13 @@ 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, false, - 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; } diff --git a/include/linux/splice.h b/include/linux/splice.h index 26e5b613ded..09a545a7dfa 100644 --- a/include/linux/splice.h +++ b/include/linux/splice.h @@ -51,7 +51,8 @@ struct partial_page { struct splice_pipe_desc { struct page **pages; /* page map */ struct partial_page *partial; /* pages[] may not be contig */ - int nr_pages; /* number of pages in map */ + int nr_pages; /* number of populated pages in map */ + unsigned int nr_pages_max; /* pages[] & partial[] arrays size */ unsigned int flags; /* splice flags */ const struct pipe_buf_operations *ops;/* ops associated with output pipe */ void (*spd_release)(struct splice_pipe_desc *, unsigned int); @@ -85,9 +86,8 @@ extern ssize_t splice_direct_to_actor(struct file *, struct splice_desc *, /* * for dynamic pipe sizing */ -extern int splice_grow_spd(struct pipe_inode_info *, struct splice_pipe_desc *); -extern void splice_shrink_spd(struct pipe_inode_info *, - struct splice_pipe_desc *); +extern int splice_grow_spd(const struct pipe_inode_info *, struct splice_pipe_desc *); +extern void splice_shrink_spd(struct splice_pipe_desc *); extern void spd_release_page(struct splice_pipe_desc *, unsigned int); extern const struct pipe_buf_operations page_cache_pipe_buf_ops; diff --git a/kernel/relay.c b/kernel/relay.c index ab56a1764d4..e8cd2027abb 100644 --- a/kernel/relay.c +++ b/kernel/relay.c @@ -1235,6 +1235,7 @@ static ssize_t subbuf_splice_actor(struct file *in, struct splice_pipe_desc spd = { .pages = pages, .nr_pages = 0, + .nr_pages_max = PIPE_DEF_BUFFERS, .partial = partial, .flags = flags, .ops = &relay_pipe_buf_ops, @@ -1302,8 +1303,8 @@ static ssize_t subbuf_splice_actor(struct file *in, ret += padding; out: - splice_shrink_spd(pipe, &spd); - return ret; + splice_shrink_spd(&spd); + return ret; } static ssize_t relay_file_splice_read(struct file *in, diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 68032c6177d..28848808222 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3609,6 +3609,7 @@ static ssize_t tracing_splice_read_pipe(struct file *filp, .pages = pages_def, .partial = partial_def, .nr_pages = 0, /* This gets updated below. */ + .nr_pages_max = PIPE_DEF_BUFFERS, .flags = flags, .ops = &tracing_pipe_buf_ops, .spd_release = tracing_spd_release_pipe, @@ -3680,7 +3681,7 @@ static ssize_t tracing_splice_read_pipe(struct file *filp, ret = splice_to_pipe(pipe, &spd); out: - splice_shrink_spd(pipe, &spd); + splice_shrink_spd(&spd); return ret; out_err: @@ -4231,6 +4232,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, struct splice_pipe_desc spd = { .pages = pages_def, .partial = partial_def, + .nr_pages_max = PIPE_DEF_BUFFERS, .flags = flags, .ops = &buffer_pipe_buf_ops, .spd_release = buffer_spd_release, @@ -4318,7 +4320,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, } ret = splice_to_pipe(pipe, &spd); - splice_shrink_spd(pipe, &spd); + splice_shrink_spd(&spd); out: return ret; } diff --git a/mm/shmem.c b/mm/shmem.c index 585bd220a21..c244e93a70f 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1577,6 +1577,7 @@ static ssize_t shmem_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, @@ -1665,7 +1666,7 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, if (spd.nr_pages) error = splice_to_pipe(pipe, &spd); - splice_shrink_spd(pipe, &spd); + splice_shrink_spd(&spd); if (error > 0) { *ppos += error; diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 016694d6248..bac3c5756d6 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1755,6 +1755,7 @@ int skb_splice_bits(struct sk_buff *skb, unsigned int offset, struct splice_pipe_desc spd = { .pages = pages, .partial = partial, + .nr_pages_max = MAX_SKB_FRAGS, .flags = flags, .ops = &sock_pipe_buf_ops, .spd_release = sock_spd_release,