Refactor struct proc_maps_private so that the fields used by PROCMAP_QUERY
ioctl are moved into a separate structure. In the next patch this allows
ioctl to reuse some of the functions used for reading /proc/pid/maps
without using file->private_data. This prevents concurrent modification
of file->private_data members by ioctl and /proc/pid/maps readers.
The change is pure code refactoring and has no functional changes.
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
fs/proc/internal.h | 15 ++++++----
fs/proc/task_mmu.c | 70 +++++++++++++++++++++++-----------------------
2 files changed, 45 insertions(+), 40 deletions(-)
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 7c235451c5ea..e2447b22592e 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -379,16 +379,21 @@ extern void proc_self_init(void);
* task_[no]mmu.c
*/
struct mem_size_stats;
-struct proc_maps_private {
- struct inode *inode;
- struct task_struct *task;
+
+struct proc_maps_query_data {
struct mm_struct *mm;
- struct vma_iterator iter;
- loff_t last_pos;
#ifdef CONFIG_PER_VMA_LOCK
bool mmap_locked;
struct vm_area_struct *locked_vma;
#endif
+};
+
+struct proc_maps_private {
+ struct inode *inode;
+ struct task_struct *task;
+ struct vma_iterator iter;
+ loff_t last_pos;
+ struct proc_maps_query_data query;
#ifdef CONFIG_NUMA
struct mempolicy *task_mempolicy;
#endif
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 3d6d8a9f13fc..509fa162760a 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -132,11 +132,11 @@ static void release_task_mempolicy(struct proc_maps_private *priv)
#ifdef CONFIG_PER_VMA_LOCK
-static void unlock_vma(struct proc_maps_private *priv)
+static void unlock_vma(struct proc_maps_query_data *query)
{
- if (priv->locked_vma) {
- vma_end_read(priv->locked_vma);
- priv->locked_vma = NULL;
+ if (query->locked_vma) {
+ vma_end_read(query->locked_vma);
+ query->locked_vma = NULL;
}
}
@@ -151,14 +151,14 @@ static inline bool lock_vma_range(struct seq_file *m,
* walking the vma tree under rcu read protection.
*/
if (m->op != &proc_pid_maps_op) {
- if (mmap_read_lock_killable(priv->mm))
+ if (mmap_read_lock_killable(priv->query.mm))
return false;
- priv->mmap_locked = true;
+ priv->query.mmap_locked = true;
} else {
rcu_read_lock();
- priv->locked_vma = NULL;
- priv->mmap_locked = false;
+ priv->query.locked_vma = NULL;
+ priv->query.mmap_locked = false;
}
return true;
@@ -166,10 +166,10 @@ static inline bool lock_vma_range(struct seq_file *m,
static inline void unlock_vma_range(struct proc_maps_private *priv)
{
- if (priv->mmap_locked) {
- mmap_read_unlock(priv->mm);
+ if (priv->query.mmap_locked) {
+ mmap_read_unlock(priv->query.mm);
} else {
- unlock_vma(priv);
+ unlock_vma(&priv->query);
rcu_read_unlock();
}
}
@@ -179,13 +179,13 @@ static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
{
struct vm_area_struct *vma;
- if (priv->mmap_locked)
+ if (priv->query.mmap_locked)
return vma_next(&priv->iter);
- unlock_vma(priv);
- vma = lock_next_vma(priv->mm, &priv->iter, last_pos);
+ unlock_vma(&priv->query);
+ vma = lock_next_vma(priv->query.mm, &priv->iter, last_pos);
if (!IS_ERR_OR_NULL(vma))
- priv->locked_vma = vma;
+ priv->query.locked_vma = vma;
return vma;
}
@@ -193,14 +193,14 @@ static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv,
loff_t pos)
{
- if (priv->mmap_locked)
+ if (priv->query.mmap_locked)
return false;
rcu_read_unlock();
- mmap_read_lock(priv->mm);
+ mmap_read_lock(priv->query.mm);
/* Reinitialize the iterator after taking mmap_lock */
vma_iter_set(&priv->iter, pos);
- priv->mmap_locked = true;
+ priv->query.mmap_locked = true;
return true;
}
@@ -210,12 +210,12 @@ static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv,
static inline bool lock_vma_range(struct seq_file *m,
struct proc_maps_private *priv)
{
- return mmap_read_lock_killable(priv->mm) == 0;
+ return mmap_read_lock_killable(priv->query.mm) == 0;
}
static inline void unlock_vma_range(struct proc_maps_private *priv)
{
- mmap_read_unlock(priv->mm);
+ mmap_read_unlock(priv->query.mm);
}
static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
@@ -258,7 +258,7 @@ static struct vm_area_struct *proc_get_vma(struct seq_file *m, loff_t *ppos)
*ppos = vma->vm_end;
} else {
*ppos = SENTINEL_VMA_GATE;
- vma = get_gate_vma(priv->mm);
+ vma = get_gate_vma(priv->query.mm);
}
return vma;
@@ -278,7 +278,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
if (!priv->task)
return ERR_PTR(-ESRCH);
- mm = priv->mm;
+ mm = priv->query.mm;
if (!mm || !mmget_not_zero(mm)) {
put_task_struct(priv->task);
priv->task = NULL;
@@ -318,7 +318,7 @@ static void *m_next(struct seq_file *m, void *v, loff_t *ppos)
static void m_stop(struct seq_file *m, void *v)
{
struct proc_maps_private *priv = m->private;
- struct mm_struct *mm = priv->mm;
+ struct mm_struct *mm = priv->query.mm;
if (!priv->task)
return;
@@ -339,9 +339,9 @@ static int proc_maps_open(struct inode *inode, struct file *file,
return -ENOMEM;
priv->inode = inode;
- priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
- if (IS_ERR_OR_NULL(priv->mm)) {
- int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
+ priv->query.mm = proc_mem_open(inode, PTRACE_MODE_READ);
+ if (IS_ERR_OR_NULL(priv->query.mm)) {
+ int err = priv->query.mm ? PTR_ERR(priv->query.mm) : -ESRCH;
seq_release_private(inode, file);
return err;
@@ -355,8 +355,8 @@ static int proc_map_release(struct inode *inode, struct file *file)
struct seq_file *seq = file->private_data;
struct proc_maps_private *priv = seq->private;
- if (priv->mm)
- mmdrop(priv->mm);
+ if (priv->query.mm)
+ mmdrop(priv->query.mm);
return seq_release_private(inode, file);
}
@@ -610,7 +610,7 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg)
if (!!karg.build_id_size != !!karg.build_id_addr)
return -EINVAL;
- mm = priv->mm;
+ mm = priv->query.mm;
if (!mm || !mmget_not_zero(mm))
return -ESRCH;
@@ -1307,7 +1307,7 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
{
struct proc_maps_private *priv = m->private;
struct mem_size_stats mss = {};
- struct mm_struct *mm = priv->mm;
+ struct mm_struct *mm = priv->query.mm;
struct vm_area_struct *vma;
unsigned long vma_start = 0, last_vma_end = 0;
int ret = 0;
@@ -1452,9 +1452,9 @@ static int smaps_rollup_open(struct inode *inode, struct file *file)
goto out_free;
priv->inode = inode;
- priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
- if (IS_ERR_OR_NULL(priv->mm)) {
- ret = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
+ priv->query.mm = proc_mem_open(inode, PTRACE_MODE_READ);
+ if (IS_ERR_OR_NULL(priv->query.mm)) {
+ ret = priv->query.mm ? PTR_ERR(priv->query.mm) : -ESRCH;
single_release(inode, file);
goto out_free;
@@ -1472,8 +1472,8 @@ static int smaps_rollup_release(struct inode *inode, struct file *file)
struct seq_file *seq = file->private_data;
struct proc_maps_private *priv = seq->private;
- if (priv->mm)
- mmdrop(priv->mm);
+ if (priv->query.mm)
+ mmdrop(priv->query.mm);
kfree(priv);
return single_release(inode, file);
--
2.50.1.565.gc32cd1483b-googOn 8/1/25 00:00, Suren Baghdasaryan wrote: > Refactor struct proc_maps_private so that the fields used by PROCMAP_QUERY > ioctl are moved into a separate structure. In the next patch this allows > ioctl to reuse some of the functions used for reading /proc/pid/maps > without using file->private_data. This prevents concurrent modification > of file->private_data members by ioctl and /proc/pid/maps readers. > > The change is pure code refactoring and has no functional changes. I think you'll need to adjust task_nommu.c as well, minimally I see it also has m_start() acceding priv->mm directly so it won't compile now? Also not sure about the naming, struct is named "proc_maps_query_data" and priv field named "query" but the read() implementation uses it too, via priv->query, although it does no PROCMAP_QUERY. Seems to me it's actually something like a mm+vma locking context? Which can be either stored in proc_maps_private for read() operations, or local on-stack for ioctl().
On Fri, Aug 1, 2025 at 3:55 AM Vlastimil Babka <vbabka@suse.cz> wrote: > > On 8/1/25 00:00, Suren Baghdasaryan wrote: > > Refactor struct proc_maps_private so that the fields used by PROCMAP_QUERY > > ioctl are moved into a separate structure. In the next patch this allows > > ioctl to reuse some of the functions used for reading /proc/pid/maps > > without using file->private_data. This prevents concurrent modification > > of file->private_data members by ioctl and /proc/pid/maps readers. > > > > The change is pure code refactoring and has no functional changes. > > I think you'll need to adjust task_nommu.c as well, minimally I see it also > has m_start() acceding priv->mm directly so it won't compile now? Ugh, yes, you are right. I'll need to adjust NOMMU code as well. And kernel test bot seems to be complaining already :) > > Also not sure about the naming, struct is named "proc_maps_query_data" and > priv field named "query" but the read() implementation uses it too, via > priv->query, although it does no PROCMAP_QUERY. > > Seems to me it's actually something like a mm+vma locking context? Which can > be either stored in proc_maps_private for read() operations, or local > on-stack for ioctl(). Yes, I struggled with the naming of this structure. Any help with this is highly appreciated.
Hi Suren,
kernel test robot noticed the following build errors:
[auto build test ERROR on 01da54f10fddf3b01c5a3b80f6b16bbad390c302]
url: https://github.com/intel-lab-lkp/linux/commits/Suren-Baghdasaryan/selftests-proc-test-PROCMAP_QUERY-ioctl-while-vma-is-concurrently-modified/20250801-060200
base: 01da54f10fddf3b01c5a3b80f6b16bbad390c302
patch link: https://lore.kernel.org/r/20250731220024.702621-3-surenb%40google.com
patch subject: [PATCH 2/3] fs/proc/task_mmu: factor out proc_maps_private fields used by PROCMAP_QUERY
config: riscv-randconfig-002-20250801 (https://download.01.org/0day-ci/archive/20250801/202508012010.9IA7JflG-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250801/202508012010.9IA7JflG-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202508012010.9IA7JflG-lkp@intel.com/
All errors (new ones prefixed by >>):
>> fs/proc/task_nommu.c:207:13: error: no member named 'mm' in 'struct proc_maps_private'
207 | mm = priv->mm;
| ~~~~ ^
fs/proc/task_nommu.c:229:31: error: no member named 'mm' in 'struct proc_maps_private'
229 | struct mm_struct *mm = priv->mm;
| ~~~~ ^
fs/proc/task_nommu.c:262:8: error: no member named 'mm' in 'struct proc_maps_private'
262 | priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
| ~~~~ ^
fs/proc/task_nommu.c:263:27: error: no member named 'mm' in 'struct proc_maps_private'
263 | if (IS_ERR_OR_NULL(priv->mm)) {
| ~~~~ ^
fs/proc/task_nommu.c:264:19: error: no member named 'mm' in 'struct proc_maps_private'
264 | int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
| ~~~~ ^
fs/proc/task_nommu.c:264:38: error: no member named 'mm' in 'struct proc_maps_private'
264 | int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
| ~~~~ ^
fs/proc/task_nommu.c:279:12: error: no member named 'mm' in 'struct proc_maps_private'
279 | if (priv->mm)
| ~~~~ ^
fs/proc/task_nommu.c:280:16: error: no member named 'mm' in 'struct proc_maps_private'
280 | mmdrop(priv->mm);
| ~~~~ ^
8 errors generated.
vim +207 fs/proc/task_nommu.c
fe441980161751 Ben Wolsieffer 2023-09-15 191
fe441980161751 Ben Wolsieffer 2023-09-15 192 static void *m_start(struct seq_file *m, loff_t *ppos)
^1da177e4c3f41 Linus Torvalds 2005-04-16 193 {
dbf8685c8e2140 David Howells 2006-09-27 194 struct proc_maps_private *priv = m->private;
fe441980161751 Ben Wolsieffer 2023-09-15 195 unsigned long last_addr = *ppos;
dbf8685c8e2140 David Howells 2006-09-27 196 struct mm_struct *mm;
0c563f14804356 Matthew Wilcox (Oracle 2022-09-06 197)
fe441980161751 Ben Wolsieffer 2023-09-15 198 /* See proc_get_vma(). Zero at the start or after lseek. */
fe441980161751 Ben Wolsieffer 2023-09-15 199 if (last_addr == -1UL)
0c563f14804356 Matthew Wilcox (Oracle 2022-09-06 200) return NULL;
dbf8685c8e2140 David Howells 2006-09-27 201
dbf8685c8e2140 David Howells 2006-09-27 202 /* pin the task and mm whilst we play with them */
2c03376d2db005 Oleg Nesterov 2014-10-09 203 priv->task = get_proc_task(priv->inode);
dbf8685c8e2140 David Howells 2006-09-27 204 if (!priv->task)
ec6fd8a4355cda Al Viro 2011-02-15 205 return ERR_PTR(-ESRCH);
dbf8685c8e2140 David Howells 2006-09-27 206
27692cd56e2aa6 Oleg Nesterov 2014-10-09 @207 mm = priv->mm;
578d7699e5c2ad Ben Wolsieffer 2023-09-14 208 if (!mm || !mmget_not_zero(mm)) {
578d7699e5c2ad Ben Wolsieffer 2023-09-14 209 put_task_struct(priv->task);
578d7699e5c2ad Ben Wolsieffer 2023-09-14 210 priv->task = NULL;
27692cd56e2aa6 Oleg Nesterov 2014-10-09 211 return NULL;
578d7699e5c2ad Ben Wolsieffer 2023-09-14 212 }
dbf8685c8e2140 David Howells 2006-09-27 213
d8ed45c5dcd455 Michel Lespinasse 2020-06-08 214 if (mmap_read_lock_killable(mm)) {
8a713e7df3352b Konstantin Khlebnikov 2019-07-11 215 mmput(mm);
578d7699e5c2ad Ben Wolsieffer 2023-09-14 216 put_task_struct(priv->task);
578d7699e5c2ad Ben Wolsieffer 2023-09-14 217 priv->task = NULL;
8a713e7df3352b Konstantin Khlebnikov 2019-07-11 218 return ERR_PTR(-EINTR);
8a713e7df3352b Konstantin Khlebnikov 2019-07-11 219 }
8a713e7df3352b Konstantin Khlebnikov 2019-07-11 220
fe441980161751 Ben Wolsieffer 2023-09-15 221 vma_iter_init(&priv->iter, mm, last_addr);
47fecca15c0944 Oleg Nesterov 2014-10-09 222
fe441980161751 Ben Wolsieffer 2023-09-15 223 return proc_get_vma(priv, ppos);
dbf8685c8e2140 David Howells 2006-09-27 224 }
dbf8685c8e2140 David Howells 2006-09-27 225
--
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