Unverified Commit c644bce6 authored by Amir Goldstein's avatar Amir Goldstein Committed by Christian Brauner
Browse files

readdir: require opt-in for d_type flags 

Commit c31f91c6 ("fuse: don't allow signals to interrupt getdents
copying") introduced the use of high bits in d_type as flags. However,
overlayfs was not adapted to handle this change.

In ovl_cache_entry_new(), the code checks if d_type == DT_CHR to
determine if an entry might be a whiteout. When fuse is used as the
lower layer and sets high bits in d_type, this comparison fails,
causing whiteout files to not be recognized properly and resulting in
incorrect overlayfs behavior.

Fix this by requiring callers of iterate_dir() to opt-in for getting
flag bits in d_type outside of S_DT_MASK.

Fixes: c31f91c6 ("fuse: don't allow signals to interrupt getdents copying")
Link: https://lore.kernel.org/all/20260107034551.439-1-luochunsheng@ustc.edu/
Link: https://github.com/containerd/stargz-snapshotter/issues/2214


Reported-by: default avatarChunsheng Luo <luochunsheng@ustc.edu>
Reviewed-by: default avatarChunsheng Luo <luochunsheng@ustc.edu>
Tested-by: default avatarChunsheng Luo <luochunsheng@ustc.edu>
Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Link: https://patch.msgid.link/20260108074522.3400998-1-amir73il@gmail.com


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 7d42f2b1

fs/readdir.c

+3 −0
Original line number Diff line number Diff line
@@ -316,6 +316,7 @@ SYSCALL_DEFINE3(getdents, unsigned int, fd, 
	struct getdents_callback buf = {

		.ctx.actor = filldir,

		.ctx.count = count,

		.ctx.dt_flags_mask = FILLDIR_FLAG_NOINTR,

		.current_dir = dirent

	};

	int error;
@@ -400,6 +401,7 @@ SYSCALL_DEFINE3(getdents64, unsigned int, fd, 
	struct getdents_callback64 buf = {

		.ctx.actor = filldir64,

		.ctx.count = count,

		.ctx.dt_flags_mask = FILLDIR_FLAG_NOINTR,

		.current_dir = dirent

	};

	int error;
@@ -569,6 +571,7 @@ COMPAT_SYSCALL_DEFINE3(getdents, unsigned int, fd, 
	struct compat_getdents_callback buf = {

		.ctx.actor = compat_filldir,

		.ctx.count = count,

		.ctx.dt_flags_mask = FILLDIR_FLAG_NOINTR,

		.current_dir = dirent,

	};

	int error;

include/linux/fs.h

+5 −1
Original line number Diff line number Diff line
@@ -1855,6 +1855,8 @@ struct dir_context { 
	 * INT_MAX  unlimited

	 */

	int count;

	/* @actor supports these flags in d_type high bits */

	unsigned int dt_flags_mask;

};



/* If OR-ed with d_type, pending signals are not checked */
@@ -3524,7 +3526,9 @@ static inline bool dir_emit(struct dir_context *ctx, 
			    const char *name, int namelen,

			    u64 ino, unsigned type)

{

	return ctx->actor(ctx, name, namelen, ctx->pos, ino, type);

	unsigned int dt_mask = S_DT_MASK | ctx->dt_flags_mask;



	return ctx->actor(ctx, name, namelen, ctx->pos, ino, type & dt_mask);

}

static inline bool dir_emit_dot(struct file *file, struct dir_context *ctx)

{