[PATCH] udf: shut up pointer cast warning

[PATCH] udf: shut up pointer cast warning

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

On 32-bit architectures, the workaround of storing the directory position
in the private_data pointer causes a warning, as loff_t does not fit in
a pointer:

fs/udf/dir.c: In function 'udf_readdir':
fs/udf/dir.c:78:25: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
   78 |         if (ctx->pos != (uintptr_t)file->private_data) {
      |                         ^
fs/udf/dir.c:211:30: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
  211 |         file->private_data = (void *)(uintptr_t)ctx->pos;
      |                              ^

An extra cast to uintptr_t shuts up the warning. This is of course
still broken if the position is ever beyond the first 2^32 bytes (4GB).

I have not found a clear information on whether directories this
large are allowed on UDF, but it seems unlikely.

Fixes: 39a464de961f ("udf: Fix crash after seekdir")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 fs/udf/dir.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/udf/dir.c b/fs/udf/dir.c
index 8ae501d27eff..5aaa82be420a 100644
--- a/fs/udf/dir.c
+++ b/fs/udf/dir.c
@@ -75,7 +75,7 @@ static int udf_readdir(struct file *file, struct dir_context *ctx)
 	 * identifying beginning of dir entry (names are under user control),
 	 * we need to scan the directory from the beginning.
 	 */
-	if (ctx->pos != (loff_t)file->private_data) {
+	if (ctx->pos != (uintptr_t)file->private_data) {
 		emit_pos = nf_pos;
 		nf_pos = 0;
 	}
@@ -208,7 +208,7 @@ static int udf_readdir(struct file *file, struct dir_context *ctx)
 
 out:
 	/* Store position where we've ended */
-	file->private_data = (void *)ctx->pos;
+	file->private_data = (void *)(uintptr_t)ctx->pos;
 	if (fibh.sbh != fibh.ebh)
 		brelse(fibh.ebh);
 	brelse(fibh.sbh);
-- 
2.29.2

Re: [PATCH] udf: shut up pointer cast warning

[Jan Kara]

On Tue 09-11-21 13:36:08, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> On 32-bit architectures, the workaround of storing the directory position
> in the private_data pointer causes a warning, as loff_t does not fit in
> a pointer:
> 
> fs/udf/dir.c: In function 'udf_readdir':
> fs/udf/dir.c:78:25: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>    78 |         if (ctx->pos != (uintptr_t)file->private_data) {
>       |                         ^
> fs/udf/dir.c:211:30: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>   211 |         file->private_data = (void *)(uintptr_t)ctx->pos;
>       |                              ^
> 
> An extra cast to uintptr_t shuts up the warning. This is of course
> still broken if the position is ever beyond the first 2^32 bytes (4GB).
> 
> I have not found a clear information on whether directories this
> large are allowed on UDF, but it seems unlikely.
> 
> Fixes: 39a464de961f ("udf: Fix crash after seekdir")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Thanks Arnd but the problem was actually (mostly theoretical) problem on
32-bita archs and furthermore I've realized it didn't completely fix the
original problem either. Yesterday I've pushed a different fix to
linux-next. So the warning should disappear.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] udf: shut up pointer cast warning

[Arnd Bergmann]

On Wed, Nov 10, 2021 at 12:00 PM Jan Kara <jack@suse.cz> wrote:
>
> Thanks Arnd but the problem was actually (mostly theoretical) problem on
> 32-bita archs and furthermore I've realized it didn't completely fix the
> original problem either. Yesterday I've pushed a different fix to
> linux-next. So the warning should disappear.

Yes, I saw your new patch and it is definitely a better fix.

Thanks,

        Arnd