From: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
To: Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
David Laight <david.laight.linux@gmail.com>
Cc: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v4] fs: Replace user_access_{begin/end} by scoped user access
Date: Wed, 18 Mar 2026 13:22:43 +0100 [thread overview]
Message-ID: <f46941437f681cc72fc5a84fa768f65b952f43c6.1773830446.git.chleroy@kernel.org> (raw)
Scoped user access reduces code complexity and seamlessly bring
masked user access on architectures that support it.
Replace user_access_begin/user_access_end blocks by
scoped user access.
Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
---
v2:
- Fix build failure with CONFIG_COMPAT
- Handled checkpatch.pl output
v3:
- Fix again build failure with CONFIG_COMPAT. I was obviously too tired when I sent out v2.
v4:
- Introduced local size var based on Linus comment on readability. Not a dirent_size() helper as suggested as both sites are different.
---
fs/readdir.c | 94 +++++++++++++++++++++-------------------------------
fs/select.c | 35 ++++++++-----------
2 files changed, 51 insertions(+), 78 deletions(-)
diff --git a/fs/readdir.c b/fs/readdir.c
index 73707b6816e9..8fa615b7e950 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -184,6 +184,7 @@ static bool fillonedir(struct dir_context *ctx, const char *name, int namlen,
struct readdir_callback *buf =
container_of(ctx, struct readdir_callback, ctx);
struct old_linux_dirent __user * dirent;
+ size_t size = offsetof(struct old_linux_dirent, d_name) + namlen + 1;
unsigned long d_ino;
if (buf->result)
@@ -198,18 +199,13 @@ static bool fillonedir(struct dir_context *ctx, const char *name, int namlen,
}
buf->result++;
dirent = buf->dirent;
- if (!user_write_access_begin(dirent,
- (unsigned long)(dirent->d_name + namlen + 1) -
- (unsigned long)dirent))
- goto efault;
- unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
- unsafe_put_user(offset, &dirent->d_offset, efault_end);
- unsafe_put_user(namlen, &dirent->d_namlen, efault_end);
- unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
- user_write_access_end();
+ scoped_user_write_access_size(dirent, size, efault) {
+ unsafe_put_user(d_ino, &dirent->d_ino, efault);
+ unsafe_put_user(offset, &dirent->d_offset, efault);
+ unsafe_put_user(namlen, &dirent->d_namlen, efault);
+ unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault);
+ }
return true;
-efault_end:
- user_write_access_end();
efault:
buf->result = -EFAULT;
return false;
@@ -287,23 +283,19 @@ static bool filldir(struct dir_context *ctx, const char *name, int namlen,
return false;
dirent = buf->current_dir;
prev = (void __user *) dirent - prev_reclen;
- if (!user_write_access_begin(prev, reclen + prev_reclen))
- goto efault;
-
- /* This might be 'dirent->d_off', but if so it will get overwritten */
- unsafe_put_user(offset, &prev->d_off, efault_end);
- unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
- unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
- unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);
- unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
- user_write_access_end();
+ scoped_user_write_access_size(prev, reclen + prev_reclen, efault) {
+ /* This might be 'dirent->d_off', but if so it will get overwritten */
+ unsafe_put_user(offset, &prev->d_off, efault);
+ unsafe_put_user(d_ino, &dirent->d_ino, efault);
+ unsafe_put_user(reclen, &dirent->d_reclen, efault);
+ unsafe_put_user(d_type, (char __user *)dirent + reclen - 1, efault);
+ unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault);
+ }
buf->current_dir = (void __user *)dirent + reclen;
buf->prev_reclen = reclen;
ctx->count -= reclen;
return true;
-efault_end:
- user_write_access_end();
efault:
buf->error = -EFAULT;
return false;
@@ -371,24 +363,20 @@ static bool filldir64(struct dir_context *ctx, const char *name, int namlen,
return false;
dirent = buf->current_dir;
prev = (void __user *)dirent - prev_reclen;
- if (!user_write_access_begin(prev, reclen + prev_reclen))
- goto efault;
-
- /* This might be 'dirent->d_off', but if so it will get overwritten */
- unsafe_put_user(offset, &prev->d_off, efault_end);
- unsafe_put_user(ino, &dirent->d_ino, efault_end);
- unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
- unsafe_put_user(d_type, &dirent->d_type, efault_end);
- unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
- user_write_access_end();
+ scoped_user_write_access_size(prev, reclen + prev_reclen, efault) {
+ /* This might be 'dirent->d_off', but if so it will get overwritten */
+ unsafe_put_user(offset, &prev->d_off, efault);
+ unsafe_put_user(ino, &dirent->d_ino, efault);
+ unsafe_put_user(reclen, &dirent->d_reclen, efault);
+ unsafe_put_user(d_type, &dirent->d_type, efault);
+ unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault);
+ }
buf->prev_reclen = reclen;
buf->current_dir = (void __user *)dirent + reclen;
ctx->count -= reclen;
return true;
-efault_end:
- user_write_access_end();
efault:
buf->error = -EFAULT;
return false;
@@ -446,6 +434,7 @@ static bool compat_fillonedir(struct dir_context *ctx, const char *name,
struct compat_readdir_callback *buf =
container_of(ctx, struct compat_readdir_callback, ctx);
struct compat_old_linux_dirent __user *dirent;
+ size_t size = offsetof(struct compat_old_linux_dirent, d_name) + namlen + 1;
compat_ulong_t d_ino;
if (buf->result)
@@ -460,18 +449,13 @@ static bool compat_fillonedir(struct dir_context *ctx, const char *name,
}
buf->result++;
dirent = buf->dirent;
- if (!user_write_access_begin(dirent,
- (unsigned long)(dirent->d_name + namlen + 1) -
- (unsigned long)dirent))
- goto efault;
- unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
- unsafe_put_user(offset, &dirent->d_offset, efault_end);
- unsafe_put_user(namlen, &dirent->d_namlen, efault_end);
- unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
- user_write_access_end();
+ scoped_user_write_access_size(dirent, size, efault) {
+ unsafe_put_user(d_ino, &dirent->d_ino, efault);
+ unsafe_put_user(offset, &dirent->d_offset, efault);
+ unsafe_put_user(namlen, &dirent->d_namlen, efault);
+ unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault);
+ }
return true;
-efault_end:
- user_write_access_end();
efault:
buf->result = -EFAULT;
return false;
@@ -543,22 +527,18 @@ static bool compat_filldir(struct dir_context *ctx, const char *name, int namlen
return false;
dirent = buf->current_dir;
prev = (void __user *) dirent - prev_reclen;
- if (!user_write_access_begin(prev, reclen + prev_reclen))
- goto efault;
-
- unsafe_put_user(offset, &prev->d_off, efault_end);
- unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
- unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
- unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);
- unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
- user_write_access_end();
+ scoped_user_write_access_size(prev, reclen + prev_reclen, efault) {
+ unsafe_put_user(offset, &prev->d_off, efault);
+ unsafe_put_user(d_ino, &dirent->d_ino, efault);
+ unsafe_put_user(reclen, &dirent->d_reclen, efault);
+ unsafe_put_user(d_type, (char __user *)dirent + reclen - 1, efault);
+ unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault);
+ }
buf->prev_reclen = reclen;
buf->current_dir = (void __user *)dirent + reclen;
ctx->count -= reclen;
return true;
-efault_end:
- user_write_access_end();
efault:
buf->error = -EFAULT;
return false;
diff --git a/fs/select.c b/fs/select.c
index e0244dbe4429..75978b18f48f 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -1004,17 +1004,17 @@ static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
fdcount = do_poll(head, &table, end_time);
poll_freewait(&table);
- if (!user_write_access_begin(ufds, nfds * sizeof(*ufds)))
- goto out_fds;
+ scoped_user_write_access_size(ufds, nfds * sizeof(*ufds), out_fds) {
+ struct pollfd __user *_ufds = ufds;
- for (walk = head; walk; walk = walk->next) {
- struct pollfd *fds = walk->entries;
- unsigned int j;
+ for (walk = head; walk; walk = walk->next) {
+ struct pollfd *fds = walk->entries;
+ unsigned int j;
- for (j = walk->len; j; fds++, ufds++, j--)
- unsafe_put_user(fds->revents, &ufds->revents, Efault);
- }
- user_write_access_end();
+ for (j = walk->len; j; fds++, _ufds++, j--)
+ unsafe_put_user(fds->revents, &_ufds->revents, out_fds);
+ }
+ }
err = fdcount;
out_fds:
@@ -1026,11 +1026,6 @@ static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
}
return err;
-
-Efault:
- user_write_access_end();
- err = -EFAULT;
- goto out_fds;
}
static long do_restart_poll(struct restart_block *restart_block)
@@ -1338,15 +1333,13 @@ static inline int get_compat_sigset_argpack(struct compat_sigset_argpack *to,
struct compat_sigset_argpack __user *from)
{
if (from) {
- if (!user_read_access_begin(from, sizeof(*from)))
- return -EFAULT;
- unsafe_get_user(to->p, &from->p, Efault);
- unsafe_get_user(to->size, &from->size, Efault);
- user_read_access_end();
+ scoped_user_read_access(from, efault) {
+ unsafe_get_user(to->p, &from->p, efault);
+ unsafe_get_user(to->size, &from->size, efault);
+ }
}
return 0;
-Efault:
- user_read_access_end();
+efault:
return -EFAULT;
}
--
2.49.0
next reply other threads:[~2026-03-18 12:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-18 12:22 Christophe Leroy (CS GROUP) [this message]
2026-03-18 14:21 ` David Laight
2026-03-18 15:34 ` Christophe Leroy (CS GROUP)
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