Patch "libfs: getdents() should return 0 after reaching EOD" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    libfs: getdents() should return 0 after reaching EOD

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     libfs-getdents-should-return-0-after-reaching-eod.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit b3f6a430f5d0109c3dbfd896a9af34a10561d69d
Author: Chuck Lever <chuck.lever@xxxxxxxxxx>
Date:   Sun Nov 19 18:56:17 2023 -0500

    libfs: getdents() should return 0 after reaching EOD
    
    [ Upstream commit 796432efab1e372d404e7a71cc6891a53f105051 ]
    
    The new directory offset helpers don't conform with the convention
    of getdents() returning no more entries once a directory file
    descriptor has reached the current end-of-directory.
    
    To address this, copy the logic from dcache_readdir() to mark the
    open directory file descriptor once EOD has been reached. Seeking
    resets the mark.
    
    Reported-by: Tavian Barnes <tavianator@xxxxxxxxxxxxxx>
    Closes: https://lore.kernel.org/linux-fsdevel/20231113180616.2831430-1-tavianator@xxxxxxxxxxxxxx/
    Fixes: 6faddda69f62 ("libfs: Add directory operations for stable offsets")
    Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/170043792492.4628.15646203084646716134.stgit@xxxxxxxxxxxxxxxxxxxxxxx
    Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/libfs.c b/fs/libfs.c
index 37f2d34ee090b..189447cf4acf5 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -396,6 +396,8 @@ static loff_t offset_dir_llseek(struct file *file, loff_t offset, int whence)
 		return -EINVAL;
 	}
 
+	/* In this case, ->private_data is protected by f_pos_lock */
+	file->private_data = NULL;
 	return vfs_setpos(file, offset, U32_MAX);
 }
 
@@ -425,7 +427,7 @@ static bool offset_dir_emit(struct dir_context *ctx, struct dentry *dentry)
 			  inode->i_ino, fs_umode_to_dtype(inode->i_mode));
 }
 
-static void offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
+static void *offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
 {
 	struct offset_ctx *so_ctx = inode->i_op->get_offset_ctx(inode);
 	XA_STATE(xas, &so_ctx->xa, ctx->pos);
@@ -434,7 +436,7 @@ static void offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
 	while (true) {
 		dentry = offset_find_next(&xas);
 		if (!dentry)
-			break;
+			return ERR_PTR(-ENOENT);
 
 		if (!offset_dir_emit(ctx, dentry)) {
 			dput(dentry);
@@ -444,6 +446,7 @@ static void offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
 		dput(dentry);
 		ctx->pos = xas.xa_index + 1;
 	}
+	return NULL;
 }
 
 /**
@@ -476,7 +479,12 @@ static int offset_readdir(struct file *file, struct dir_context *ctx)
 	if (!dir_emit_dots(file, ctx))
 		return 0;
 
-	offset_iterate_dir(d_inode(dir), ctx);
+	/* In this case, ->private_data is protected by f_pos_lock */
+	if (ctx->pos == 2)
+		file->private_data = NULL;
+	else if (file->private_data == ERR_PTR(-ENOENT))
+		return 0;
+	file->private_data = offset_iterate_dir(d_inode(dir), ctx);
 	return 0;
 }