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readdir: require opt-in for d_type flags

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Commit c31f91c6af ("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: c31f91c6af ("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: Chunsheng Luo <luochunsheng@ustc.edu>
Reviewed-by: Chunsheng Luo <luochunsheng@ustc.edu>
Tested-by: Chunsheng Luo <luochunsheng@ustc.edu>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://patch.msgid.link/20260108074522.3400998-1-amir73il@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Amir Goldstein 2026-01-08 08:45:22 +01:00 • committed by Christian Brauner
parent 7d42f2b1cc
commit c644bce62b
No known key found for this signature in database
GPG key ID: 91C61BC06578DCA2
2 changed files with 8 additions and 1 deletions
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3
fs/readdir.c
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@ -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;

6
include/linux/fs.h
View file

@ -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)
{