diff options
| author | Christian Brauner <brauner@kernel.org> | 2024-08-30 16:04:55 +0300 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2024-09-12 12:58:44 +0300 |
| commit | b4dba2efa8106002076b070fdff24ed6bf1ea87b (patch) | |
| tree | 2649e5f1c75004fe1382143fe7f26d363ad74062 | |
| parent | ceaa5e80db7c73321c89fda39c3c8c78817aecd2 (diff) | |
| download | linux-b4dba2efa8106002076b070fdff24ed6bf1ea87b.tar.xz | |
proc: store cookie in private data
Store the cookie to detect concurrent seeks on directories in
file->private_data.
Link: https://lore.kernel.org/r/20240830-vfs-file-f_version-v1-14-6d3e4816aa7b@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
| -rw-r--r-- | fs/proc/base.c | 30 |
1 files changed, 24 insertions, 6 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c index 72a1acd03675..988f6bbfc4bd 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3870,12 +3870,12 @@ static int proc_task_readdir(struct file *file, struct dir_context *ctx) if (!dir_emit_dots(file, ctx)) return 0; - /* f_version caches the tgid value that the last readdir call couldn't - * return. lseek aka telldir automagically resets f_version to 0. + /* We cache the tgid value that the last readdir call couldn't + * return and lseek resets it to 0. */ ns = proc_pid_ns(inode->i_sb); - tid = (int)file->f_version; - file->f_version = 0; + tid = (int)(intptr_t)file->private_data; + file->private_data = NULL; for (task = first_tid(proc_pid(inode), tid, ctx->pos - 2, ns); task; task = next_tid(task), ctx->pos++) { @@ -3890,7 +3890,7 @@ static int proc_task_readdir(struct file *file, struct dir_context *ctx) proc_task_instantiate, task, NULL)) { /* returning this tgid failed, save it as the first * pid for the next readir call */ - file->f_version = (u64)tid; + file->private_data = (void *)(intptr_t)tid; put_task_struct(task); break; } @@ -3915,6 +3915,24 @@ static int proc_task_getattr(struct mnt_idmap *idmap, return 0; } +/* + * proc_task_readdir() set @file->private_data to a positive integer + * value, so casting that to u64 is safe. generic_llseek_cookie() will + * set @cookie to 0, so casting to an int is safe. The WARN_ON_ONCE() is + * here to catch any unexpected change in behavior either in + * proc_task_readdir() or generic_llseek_cookie(). + */ +static loff_t proc_dir_llseek(struct file *file, loff_t offset, int whence) +{ + u64 cookie = (u64)(intptr_t)file->private_data; + loff_t off; + + off = generic_llseek_cookie(file, offset, whence, &cookie); + WARN_ON_ONCE(cookie > INT_MAX); + file->private_data = (void *)(intptr_t)cookie; /* serialized by f_pos_lock */ + return off; +} + static const struct inode_operations proc_task_inode_operations = { .lookup = proc_task_lookup, .getattr = proc_task_getattr, @@ -3925,7 +3943,7 @@ static const struct inode_operations proc_task_inode_operations = { static const struct file_operations proc_task_operations = { .read = generic_read_dir, .iterate_shared = proc_task_readdir, - .llseek = generic_file_llseek, + .llseek = proc_dir_llseek, }; void __init set_proc_pid_nlink(void) |