5.4-stable review patch. If anyone has any objections, please let me know.
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From: Sergey Bashirov sergeybashirov@gmail.com
[ Upstream commit 9768797c219326699778fba9cd3b607b2f1e7950 ]
The error occurs on the third attempt to encode extents. When function ext_tree_prepare_commit() reallocates a larger buffer to retry encoding extents, the "layoutupdate_pages" page array is initialized only after the retry loop. But ext_tree_free_commitdata() is called on every iteration and tries to put pages in the array, thus dereferencing uninitialized pointers.
An additional problem is that there is no limit on the maximum possible buffer_size. When there are too many extents, the client may create a layoutcommit that is larger than the maximum possible RPC size accepted by the server.
During testing, we observed two typical scenarios. First, one memory page for extents is enough when we work with small files, append data to the end of the file, or preallocate extents before writing. But when we fill a new large file without preallocating, the number of extents can be huge, and counting the number of written extents in ext_tree_encode_commit() does not help much. Since this number increases even more between unlocking and locking of ext_tree, the reallocated buffer may not be large enough again and again.
Co-developed-by: Konstantin Evtushenko koevtushenko@yandex.com Signed-off-by: Konstantin Evtushenko koevtushenko@yandex.com Signed-off-by: Sergey Bashirov sergeybashirov@gmail.com Reviewed-by: Christoph Hellwig hch@lst.de Link: https://lore.kernel.org/r/20250630183537.196479-2-sergeybashirov@gmail.com Signed-off-by: Trond Myklebust trond.myklebust@hammerspace.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nfs/blocklayout/extent_tree.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/fs/nfs/blocklayout/extent_tree.c b/fs/nfs/blocklayout/extent_tree.c index 7a57ff2528af..055ec818eaaa 100644 --- a/fs/nfs/blocklayout/extent_tree.c +++ b/fs/nfs/blocklayout/extent_tree.c @@ -552,6 +552,15 @@ static int ext_tree_encode_commit(struct pnfs_block_layout *bl, __be32 *p, return ret; }
+/** + * ext_tree_prepare_commit - encode extents that need to be committed + * @arg: layout commit data + * + * Return values: + * %0: Success, all required extents are encoded + * %-ENOSPC: Some extents are encoded, but not all, due to RPC size limit + * %-ENOMEM: Out of memory, extents not encoded + */ int ext_tree_prepare_commit(struct nfs4_layoutcommit_args *arg) { @@ -568,12 +577,12 @@ ext_tree_prepare_commit(struct nfs4_layoutcommit_args *arg) start_p = page_address(arg->layoutupdate_page); arg->layoutupdate_pages = &arg->layoutupdate_page;
-retry: - ret = ext_tree_encode_commit(bl, start_p + 1, buffer_size, &count, &arg->lastbytewritten); + ret = ext_tree_encode_commit(bl, start_p + 1, buffer_size, + &count, &arg->lastbytewritten); if (unlikely(ret)) { ext_tree_free_commitdata(arg, buffer_size);
- buffer_size = ext_tree_layoutupdate_size(bl, count); + buffer_size = NFS_SERVER(arg->inode)->wsize; count = 0;
arg->layoutupdate_pages = @@ -588,7 +597,8 @@ ext_tree_prepare_commit(struct nfs4_layoutcommit_args *arg) return -ENOMEM; }
- goto retry; + ret = ext_tree_encode_commit(bl, start_p + 1, buffer_size, + &count, &arg->lastbytewritten); }
*start_p = cpu_to_be32(count); @@ -608,7 +618,7 @@ ext_tree_prepare_commit(struct nfs4_layoutcommit_args *arg) }
dprintk("%s found %zu ranges\n", __func__, count); - return 0; + return ret; }
void