Hi,
在 2024/11/11 8:52, cel@xxxxxxxxxx 写道:
From: yangerkun <yangerkun@xxxxxxxxxx>
[ Upstream commit 64a7ce76fb901bf9f9c36cf5d681328fc0fd4b5a ]
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
Please notice this requires last_index should never overflow, otherwise
readdir will be messed up.
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@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240731043835.1828697-1-yangerkun@xxxxxxxxxx
Reviewed-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
[brauner: only update last_index after seek when offset is zero like Jan suggested]
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Link: https://nvd.nist.gov/vuln/detail/CVE-2024-46701
[ cel: adjusted to apply to origin/linux-6.6.y ]
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
fs/libfs.c | 37 +++++++++++++++++++++++++------------
1 file changed, 25 insertions(+), 12 deletions(-)
diff --git a/fs/libfs.c b/fs/libfs.c
index a87005c89534..b59ff0dfea1f 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -449,6 +449,14 @@ void simple_offset_destroy(struct offset_ctx *octx)
xa_destroy(&octx->xa);
}
+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;
+}
Looks like xarray is still used.
I'm in the cc list ,so I assume you saw my set, then I don't know why
you're ignoring my concerns.
1) next_offset is 32-bit and can overflow in a long-time running
machine.
2) Once next_offset overflows, readdir will skip the files that offset
is bigger.
Thanks,
Kuai
+
/**
* offset_dir_llseek - Advance the read position of a directory descriptor
* @file: an open directory whose position is to be updated
@@ -462,6 +470,9 @@ 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;
@@ -475,8 +486,9 @@ 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;
- return vfs_setpos(file, offset, U32_MAX);
+ if (!offset)
+ file->private_data = (void *)ctx->next_offset;
+ return vfs_setpos(file, offset, LONG_MAX);
}
static struct dentry *offset_find_next(struct xa_state *xas)
@@ -505,7 +517,7 @@ 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 *so_ctx = inode->i_op->get_offset_ctx(inode);
XA_STATE(xas, &so_ctx->xa, ctx->pos);
@@ -514,17 +526,21 @@ static void *offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
while (true) {
dentry = offset_find_next(&xas);
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;
}
dput(dentry);
ctx->pos = xas.xa_index + 1;
}
- return NULL;
}
/**
@@ -551,22 +567,19 @@ 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,
