Subject: [RFC PATCH 05/21] ubifs: Pass worst-case buffer size to compression routines

From: Ard Biesheuvel <[email-masked]>
Date: Tue, 18 Jul 2023 14:58:31 +0200

Currently, the ubifs code allocates a worst case buffer size to
recompress a data node, but does not pass the size of that buffer to the
compression code. This means that the compression code will never use
the additional space, and might fail spuriously due to lack of space.

So let's multiply out_len by WORST_COMPR_FACTOR after allocating the
buffer. Doing so is guaranteed not to overflow, given that the preceding
kmalloc_array() call would have failed otherwise.

Signed-off-by: Ard Biesheuvel <[email-masked]>
---
 fs/ubifs/journal.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/ubifs/journal.c b/fs/ubifs/journal.c
index dc52ac0f4a345f30..4e5961878f336033 100644
--- a/fs/ubifs/journal.c
+++ b/fs/ubifs/journal.c
@@ -1493,6 +1493,8 @@ static int truncate_data_node(const struct ubifs_info *c, const struct inode *in
 	if (!buf)
 		return -ENOMEM;
 
+	out_len *= WORST_COMPR_FACTOR;
+
 	dlen = le32_to_cpu(dn->ch.len) - UBIFS_DATA_NODE_SZ;
 	data_size = dn_size - UBIFS_DATA_NODE_SZ;
 	compr_type = le16_to_cpu(dn->compr_type);
-- 
2.39.2