fuse: don't allow signals to interrupt getdents copying

When getting the directory contents, the entries are first fetched to a
kernel buffer, then they are copied to userspace with dir_emit().  This
second phase is non-blocking as long as the userspace buffer is not paged
out, making it interruptible makes zero sense.

Overload d_type as flags, since it only uses 4 bits from 32.

Reviewed-by: Bernd Schubert <bschubert@ddn.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Link: https://lore.kernel.org/20250513112335.1473177-1-mszeredi@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/fuse/readdir.c b/fs/fuse/readdir.c
index 17ce9636a2b1a4674e29e4050f08deca7ed10d72..edcd6f18a8a81e7f448cfb8e3a9d8bca421c6fc3 100644 (file)
--- a/fs/fuse/readdir.c
+++ b/fs/fuse/readdir.c
@@ -120,7 +120,7 @@ static bool fuse_emit(struct file *file, struct dir_context *ctx,
                fuse_add_dirent_to_cache(file, dirent, ctx->pos);
 
        return dir_emit(ctx, dirent->name, dirent->namelen, dirent->ino,
-                       dirent->type);
+                       dirent->type | FILLDIR_FLAG_NOINTR);
 }
 
 static int parse_dirfile(char *buf, size_t nbytes, struct file *file,
@@ -419,7 +419,7 @@ static enum fuse_parse_result fuse_parse_cache(struct fuse_file *ff,
                if (ff->readdir.pos == ctx->pos) {
                        res = FOUND_SOME;
                        if (!dir_emit(ctx, dirent->name, dirent->namelen,
-                                     dirent->ino, dirent->type))
+                                     dirent->ino, dirent->type | FILLDIR_FLAG_NOINTR))
                                return FOUND_ALL;
                        ctx->pos = dirent->off;
                }

diff --git a/fs/readdir.c b/fs/readdir.c
index 0038efda417bbe77a82cd008e9ffe06ec18bb8ad..857d402bc53159670a2d6f5c768c530c5ca2dcb2 100644 (file)
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -266,6 +266,10 @@ static bool filldir(struct dir_context *ctx, const char *name, int namlen,
        int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
                sizeof(long));
        int prev_reclen;
+       unsigned int flags = d_type;
+
+       BUILD_BUG_ON(FILLDIR_FLAG_NOINTR & S_DT_MASK);
+       d_type &= S_DT_MASK;
 
        buf->error = verify_dirent_name(name, namlen);
        if (unlikely(buf->error))
@@ -279,7 +283,7 @@ static bool filldir(struct dir_context *ctx, const char *name, int namlen,
                return false;
        }
        prev_reclen = buf->prev_reclen;
-       if (prev_reclen && signal_pending(current))
+       if (!(flags & FILLDIR_FLAG_NOINTR) && prev_reclen && signal_pending(current))
                return false;
        dirent = buf->current_dir;
        prev = (void __user *) dirent - prev_reclen;
@@ -351,6 +355,10 @@ static bool filldir64(struct dir_context *ctx, const char *name, int namlen,
        int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
                sizeof(u64));
        int prev_reclen;
+       unsigned int flags = d_type;
+
+       BUILD_BUG_ON(FILLDIR_FLAG_NOINTR & S_DT_MASK);
+       d_type &= S_DT_MASK;
 
        buf->error = verify_dirent_name(name, namlen);
        if (unlikely(buf->error))
@@ -359,7 +367,7 @@ static bool filldir64(struct dir_context *ctx, const char *name, int namlen,
        if (reclen > buf->count)
                return false;
        prev_reclen = buf->prev_reclen;
-       if (prev_reclen && signal_pending(current))
+       if (!(flags & FILLDIR_FLAG_NOINTR) && prev_reclen && signal_pending(current))
                return false;
        dirent = buf->current_dir;
        prev = (void __user *)dirent - prev_reclen;
@@ -513,6 +521,10 @@ static bool compat_filldir(struct dir_context *ctx, const char *name, int namlen
        int reclen = ALIGN(offsetof(struct compat_linux_dirent, d_name) +
                namlen + 2, sizeof(compat_long_t));
        int prev_reclen;
+       unsigned int flags = d_type;
+
+       BUILD_BUG_ON(FILLDIR_FLAG_NOINTR & S_DT_MASK);
+       d_type &= S_DT_MASK;
 
        buf->error = verify_dirent_name(name, namlen);
        if (unlikely(buf->error))
@@ -526,7 +538,7 @@ static bool compat_filldir(struct dir_context *ctx, const char *name, int namlen
                return false;
        }
        prev_reclen = buf->prev_reclen;
-       if (prev_reclen && signal_pending(current))
+       if (!(flags & FILLDIR_FLAG_NOINTR) && prev_reclen && signal_pending(current))
                return false;
        dirent = buf->current_dir;
        prev = (void __user *) dirent - prev_reclen;

diff --git a/include/linux/fs.h b/include/linux/fs.h
index cf7208500cee303af282415d0ded3699f8861f7a..c8b5af17060e463d1e14914e78ee2304e6e5e6b6 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2073,6 +2073,9 @@ struct dir_context {
        loff_t pos;
 };
 
+/* If OR-ed with d_type, pending signals are not checked */
+#define FILLDIR_FLAG_NOINTR    0x1000
+
 /*
  * These flags let !MMU mmap() govern direct device mapping vs immediate
  * copying more easily for MAP_PRIVATE, especially for ROM filesystems.