From: yangerkun yangerkun@huawei.com
commit 64a7ce76fb901bf9f9c36cf5d681328fc0fd4b5a upstream.
After we switch tmpfs dir operations from simple_dir_operations to simple_offset_dir_operations, every rename happened will fill new dentry to dest dir's maple tree(&SHMEM_I(inode)->dir_offsets->mt) with a free key starting with octx->newx_offset, and then set newx_offset equals to free key + 1. This will lead to infinite readdir combine with rename happened at the same time, which fail generic/736 in xfstests(detail show as below).
1. create 5000 files(1 2 3...) under one dir 2. call readdir(man 3 readdir) once, and get one entry 3. rename(entry, "TEMPFILE"), then rename("TEMPFILE", entry) 4. loop 2~3, until readdir return nothing or we loop too many times(tmpfs break test with the second condition)
We choose the same logic what commit 9b378f6ad48cf ("btrfs: fix infinite directory reads") to fix it, record the last_index when we open dir, and do not emit the entry which index >= last_index. The file->private_data now used in offset dir can use directly to do this, and we also update the last_index when we llseek the dir file.
Fixes: a2e459555c5f ("shmem: stable directory offsets") Signed-off-by: yangerkun yangerkun@huawei.com Link: https://lore.kernel.org/r/20240731043835.1828697-1-yangerkun@huawei.com Reviewed-by: Chuck Lever chuck.lever@oracle.com [brauner: only update last_index after seek when offset is zero like Jan suggested] Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Yu Kuai yukuai3@huawei.com --- fs/libfs.c | 35 ++++++++++++++++++++++++----------- 1 file changed, 24 insertions(+), 11 deletions(-)
diff --git a/fs/libfs.c b/fs/libfs.c index 98731178a3c1..fd5d30c798de 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -405,6 +405,14 @@ void simple_offset_destroy(struct offset_ctx *octx) mtree_destroy(&octx->mt); }
+static int offset_dir_open(struct inode *inode, struct file *file) +{ + struct offset_ctx *ctx = inode->i_op->get_offset_ctx(inode); + + file->private_data = (void *)ctx->next_offset; + return 0; +} + /** * offset_dir_llseek - Advance the read position of a directory descriptor * @file: an open directory whose position is to be updated @@ -418,6 +426,9 @@ void simple_offset_destroy(struct offset_ctx *octx) */ static loff_t offset_dir_llseek(struct file *file, loff_t offset, int whence) { + struct inode *inode = file->f_inode; + struct offset_ctx *ctx = inode->i_op->get_offset_ctx(inode); + switch (whence) { case SEEK_CUR: offset += file->f_pos; @@ -431,7 +442,8 @@ static loff_t offset_dir_llseek(struct file *file, loff_t offset, int whence) }
/* In this case, ->private_data is protected by f_pos_lock */ - file->private_data = NULL; + if (!offset) + file->private_data = (void *)ctx->next_offset; return vfs_setpos(file, offset, LONG_MAX); }
@@ -462,7 +474,7 @@ 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, long last_index) { struct offset_ctx *octx = inode->i_op->get_offset_ctx(inode); struct dentry *dentry; @@ -470,17 +482,21 @@ static void *offset_iterate_dir(struct inode *inode, struct dir_context *ctx) while (true) { dentry = offset_find_next(octx, ctx->pos); if (!dentry) - return ERR_PTR(-ENOENT); + return; + + if (dentry2offset(dentry) >= last_index) { + dput(dentry); + return; + }
if (!offset_dir_emit(ctx, dentry)) { dput(dentry); - break; + return; }
ctx->pos = dentry2offset(dentry) + 1; dput(dentry); } - return NULL; }
/** @@ -507,22 +523,19 @@ static void *offset_iterate_dir(struct inode *inode, struct dir_context *ctx) static int offset_readdir(struct file *file, struct dir_context *ctx) { struct dentry *dir = file->f_path.dentry; + long last_index = (long)file->private_data;
lockdep_assert_held(&d_inode(dir)->i_rwsem);
if (!dir_emit_dots(file, ctx)) return 0;
- /* In this case, ->private_data is protected by f_pos_lock */ - if (ctx->pos == DIR_OFFSET_MIN) - file->private_data = NULL; - else if (file->private_data == ERR_PTR(-ENOENT)) - return 0; - file->private_data = offset_iterate_dir(d_inode(dir), ctx); + offset_iterate_dir(d_inode(dir), ctx, last_index); return 0; }
const struct file_operations simple_offset_dir_operations = { + .open = offset_dir_open, .llseek = offset_dir_llseek, .iterate_shared = offset_readdir, .read = generic_read_dir,