5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> [ Upstream commit 120ce2b0cd52abe73e8b16c23461eb14df5a87d8 ] To make it easy to tell where files->file_lock protection is being used when looking up a file create files_lookup_fd_locked. Only allow this function to be called with the file_lock held. Update the callers of fcheck and fcheck_files that are called with the files->file_lock held to call files_lookup_fd_locked instead. Hopefully this makes it easier to quickly understand what is going on. The need for better names became apparent in the last round of discussion of this set of changes[1]. [1] https://lkml.kernel.org/r/CAHk-=wj8BQbgJFLa+J0e=iT-1qpmCRTbPAJ8gd6MJQ=kbRPqyQ@xxxxxxxxxxxxxx Link: https://lkml.kernel.org/r/20201120231441.29911-8-ebiederm@xxxxxxxxxxxx Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/file.c | 2 +- fs/locks.c | 14 ++++++++------ fs/proc/fd.c | 2 +- include/linux/fdtable.h | 7 +++++++ 4 files changed, 17 insertions(+), 8 deletions(-) diff --git a/fs/file.c b/fs/file.c index eb1e2b7220ac6..6a6b03ce4ad69 100644 --- a/fs/file.c +++ b/fs/file.c @@ -1158,7 +1158,7 @@ static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags) spin_lock(&files->file_lock); err = expand_files(files, newfd); - file = fcheck(oldfd); + file = files_lookup_fd_locked(files, oldfd); if (unlikely(!file)) goto Ebadf; if (unlikely(err < 0)) { diff --git a/fs/locks.c b/fs/locks.c index cbb5701ce9f37..873f97504bddf 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -2536,14 +2536,15 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd, */ if (!error && file_lock->fl_type != F_UNLCK && !(file_lock->fl_flags & FL_OFDLCK)) { + struct files_struct *files = current->files; /* * We need that spin_lock here - it prevents reordering between * update of i_flctx->flc_posix and check for it done in * close(). rcu_read_lock() wouldn't do. */ - spin_lock(¤t->files->file_lock); - f = fcheck(fd); - spin_unlock(¤t->files->file_lock); + spin_lock(&files->file_lock); + f = files_lookup_fd_locked(files, fd); + spin_unlock(&files->file_lock); if (f != filp) { file_lock->fl_type = F_UNLCK; error = do_lock_file_wait(filp, cmd, file_lock); @@ -2667,14 +2668,15 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd, */ if (!error && file_lock->fl_type != F_UNLCK && !(file_lock->fl_flags & FL_OFDLCK)) { + struct files_struct *files = current->files; /* * We need that spin_lock here - it prevents reordering between * update of i_flctx->flc_posix and check for it done in * close(). rcu_read_lock() wouldn't do. */ - spin_lock(¤t->files->file_lock); - f = fcheck(fd); - spin_unlock(¤t->files->file_lock); + spin_lock(&files->file_lock); + f = files_lookup_fd_locked(files, fd); + spin_unlock(&files->file_lock); if (f != filp) { file_lock->fl_type = F_UNLCK; error = do_lock_file_wait(filp, cmd, file_lock); diff --git a/fs/proc/fd.c b/fs/proc/fd.c index d58960f6ee524..2cca9bca3b3a3 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -35,7 +35,7 @@ static int seq_show(struct seq_file *m, void *v) unsigned int fd = proc_fd(m->private); spin_lock(&files->file_lock); - file = fcheck_files(files, fd); + file = files_lookup_fd_locked(files, fd); if (file) { struct fdtable *fdt = files_fdtable(files); diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index 10e75b4c30a43..87be704268d26 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -91,6 +91,13 @@ static inline struct file *files_lookup_fd_raw(struct files_struct *files, unsig return NULL; } +static inline struct file *files_lookup_fd_locked(struct files_struct *files, unsigned int fd) +{ + RCU_LOCKDEP_WARN(!lockdep_is_held(&files->file_lock), + "suspicious rcu_dereference_check() usage"); + return files_lookup_fd_raw(files, fd); +} + static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd) { RCU_LOCKDEP_WARN(!rcu_read_lock_held() && -- 2.43.0
