e60aa5da14
When opening a directory we find what's the index of its last entry and
then store it in the directory's file handle private data (struct
btrfs_file_private::last_index), so that in the case new directory entries
are added to a directory after an opendir(3) call we don't end up in an
infinite loop (see commit 9b378f6ad48c ("btrfs: fix infinite directory
reads")) when calling readdir(3).
However once rewinddir(3) is called, POSIX states [1] that any new
directory entries added after the previous opendir(3) call, must be
returned by subsequent calls to readdir(3):
"The rewinddir() function shall reset the position of the directory
stream to which dirp refers to the beginning of the directory.
It shall also cause the directory stream to refer to the current
state of the corresponding directory, as a call to opendir() would
have done."
We currently don't refresh the last_index field of the struct
btrfs_file_private associated to the directory, so after a rewinddir(3)
we are not returning any new entries added after the opendir(3) call.
Fix this by finding the current last index of the directory when llseek
is called against the directory.
This can be reproduced by the following C program provided by Ian Johnson:
#include <dirent.h>
#include <stdio.h>
int main(void) {
DIR *dir = opendir("test");
FILE *file;
file = fopen("test/1", "w");
fwrite("1", 1, 1, file);
fclose(file);
file = fopen("test/2", "w");
fwrite("2", 1, 1, file);
fclose(file);
rewinddir(dir);
struct dirent *entry;
while ((entry = readdir(dir))) {
printf("%s\n", entry->d_name);
}
closedir(dir);
return 0;
}
Reported-by: Ian Johnson <ian@ianjohnson.dev>
Link: https://lore.kernel.org/linux-btrfs/YR1P0S.NGASEG570GJ8@ianjohnson.dev/
Fixes: 9b378f6ad48c ("btrfs: fix infinite directory reads")
CC: stable@vger.kernel.org # 6.5+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.