linux-kernel - [PATCHv2 5.15] udf: Allocate name buffer in directory iterator on heap

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Message-ID: <20241115060859.2453211-1-senozhatsky@chromium.org>
Date: Fri, 15 Nov 2024 15:08:48 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: stable@...r.kernel.org
Cc: Jan Kara <jack@...e.cz>,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	kernel test robot <lkp@...el.com>
Subject: [PATCHv2 5.15] udf: Allocate name buffer in directory iterator on heap

From: Jan Kara <jack@...e.cz>

[ Upstream commit 0aba4860b0d0216a1a300484ff536171894d49d8 ]

Currently we allocate name buffer in directory iterators (struct
udf_fileident_iter) on stack. These structures are relatively large
(some 360 bytes on 64-bit architectures). For udf_rename() which needs
to keep three of these structures in parallel the stack usage becomes
rather heavy - 1536 bytes in total. Allocate the name buffer in the
iterator from heap to avoid excessive stack usage.

Link: https://lore.kernel.org/all/202212200558.lK9x1KW0-lkp@intel.com
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Jan Kara <jack@...e.cz>
[ senozhatsky: explicitly include slab.h to address build
  failure reported by sashal@ ]
Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
---
 fs/udf/directory.c | 24 ++++++++++++++++--------
 fs/udf/udfdecl.h   |  2 +-
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/fs/udf/directory.c b/fs/udf/directory.c
index e97ffae07833..a30898debdd1 100644
--- a/fs/udf/directory.c
+++ b/fs/udf/directory.c
@@ -19,6 +19,7 @@
 #include <linux/bio.h>
 #include <linux/crc-itu-t.h>
 #include <linux/iversion.h>
+#include <linux/slab.h>
 
 static int udf_verify_fi(struct udf_fileident_iter *iter)
 {
@@ -248,9 +249,14 @@ int udf_fiiter_init(struct udf_fileident_iter *iter, struct inode *dir,
 	iter->elen = 0;
 	iter->epos.bh = NULL;
 	iter->name = NULL;
+	iter->namebuf = kmalloc(UDF_NAME_LEN_CS0, GFP_KERNEL);
+	if (!iter->namebuf)
+		return -ENOMEM;
 
-	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB)
-		return udf_copy_fi(iter);
+	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
+		err = udf_copy_fi(iter);
+		goto out;
+	}
 
 	if (inode_bmap(dir, iter->pos >> dir->i_blkbits, &iter->epos,
 		       &iter->eloc, &iter->elen, &iter->loffset) !=
@@ -260,17 +266,17 @@ int udf_fiiter_init(struct udf_fileident_iter *iter, struct inode *dir,
 		udf_err(dir->i_sb,
 			"position %llu not allocated in directory (ino %lu)\n",
 			(unsigned long long)pos, dir->i_ino);
-		return -EFSCORRUPTED;
+		err = -EFSCORRUPTED;
+		goto out;
 	}
 	err = udf_fiiter_load_bhs(iter);
 	if (err < 0)
-		return err;
+		goto out;
 	err = udf_copy_fi(iter);
-	if (err < 0) {
+out:
+	if (err < 0)
 		udf_fiiter_release(iter);
-		return err;
-	}
-	return 0;
+	return err;
 }
 
 int udf_fiiter_advance(struct udf_fileident_iter *iter)
@@ -307,6 +313,8 @@ void udf_fiiter_release(struct udf_fileident_iter *iter)
 	brelse(iter->bh[0]);
 	brelse(iter->bh[1]);
 	iter->bh[0] = iter->bh[1] = NULL;
+	kfree(iter->namebuf);
+	iter->namebuf = NULL;
 }
 
 static void udf_copy_to_bufs(void *buf1, int len1, void *buf2, int len2,
diff --git a/fs/udf/udfdecl.h b/fs/udf/udfdecl.h
index f764b4d15094..d35aa42bb577 100644
--- a/fs/udf/udfdecl.h
+++ b/fs/udf/udfdecl.h
@@ -99,7 +99,7 @@ struct udf_fileident_iter {
 	struct extent_position epos;	/* Position after the above extent */
 	struct fileIdentDesc fi;	/* Copied directory entry */
 	uint8_t *name;			/* Pointer to entry name */
-	uint8_t namebuf[UDF_NAME_LEN_CS0]; /* Storage for entry name in case
+	uint8_t *namebuf;		/* Storage for entry name in case
 					 * the name is split between two blocks
 					 */
 };
-- 
2.47.0.338.g60cca15819-goog