* Forwarded: [PATCH] namei: fix parent inode unlock in end_creating_path()
2026-03-05 6:39 [syzbot] [exfat?] [gfs2?] WARNING in filename_symlinkat syzbot
@ 2026-03-06 4:38 ` syzbot
2026-03-06 5:22 ` Forwarded: [PATCH] namei: add debug printk to trace parent inode lock state syzbot
` (8 subsequent siblings)
9 siblings, 0 replies; 21+ messages in thread
From: syzbot @ 2026-03-06 4:38 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] namei: fix parent inode unlock in end_creating_path()
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
end_creating_path() calls end_dirop() which unlocks
dentry->d_parent->d_inode. However, the lock was originally acquired on
path->dentry by start_dirop() inside filename_create(). If a concurrent
operation such as renameat2(RENAME_EXCHANGE) modifies the dentry tree
between lock and unlock, dentry->d_parent may no longer point to the
originally locked inode, causing an unbalanced unlock.
Fix this by unlocking path->dentry directly in end_creating_path()
instead of deriving the parent from the child dentry. This ensures the
lock and unlock always operate on the same inode regardless of
concurrent dentry tree modifications.
Reported-by: syzbot+2ed46b6b748df855347f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2ed46b6b748df855347f
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
---
fs/namei.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/namei.c b/fs/namei.c
index 58f715f7657e..c861de965d86 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4959,7 +4959,10 @@ EXPORT_SYMBOL(start_creating_path);
*/
void end_creating_path(const struct path *path, struct dentry *dentry)
{
- end_creating(dentry);
+ if (!IS_ERR(dentry)) {
+ inode_unlock(d_inode(path->dentry));
+ dput(dentry);
+ }
mnt_drop_write(path->mnt);
path_put(path);
}
--
2.43.0
^ permalink raw reply related [flat|nested] 21+ messages in thread* Forwarded: [PATCH] namei: add debug printk to trace parent inode lock state
2026-03-05 6:39 [syzbot] [exfat?] [gfs2?] WARNING in filename_symlinkat syzbot
2026-03-06 4:38 ` Forwarded: [PATCH] namei: fix parent inode unlock in end_creating_path() syzbot
@ 2026-03-06 5:22 ` syzbot
2026-03-06 6:25 ` Forwarded: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode syzbot
` (7 subsequent siblings)
9 siblings, 0 replies; 21+ messages in thread
From: syzbot @ 2026-03-06 5:22 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] namei: add debug printk to trace parent inode lock state
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Add debug printk statements to trace the parent directory inode rwsem
state through the symlink creation path. This helps identify which
component is dropping the parent inode's i_rwsem between start_dirop()
and end_dirop(), causing the unbalanced unlock WARNING in
filename_symlinkat().
The printk traces:
- rwsem owner/count after start_dirop() acquires the lock
- rwsem owner/count after vfs_symlink() returns
- rwsem owner/count at end_dirop() just before the unlock
- dentry->d_parent and path->dentry at each point
This is a temporary diagnostic patch and should be reverted once the
root cause is identified.
Reported-by: syzbot+2ed46b6b748df855347f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2ed46b6b748df855347f
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
---
fs/namei.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 58f715f7657e..9584ff6dff47 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2944,6 +2944,11 @@ struct dentry *start_dirop(struct dentry *parent, struct qstr *name,
void end_dirop(struct dentry *de)
{
if (!IS_ERR(de)) {
+ struct inode *dir = d_inode(de->d_parent);
+ pr_warn("DEBUG: end_dirop: de=%px parent=%px inode=%px rwsem count=%ld owner=%px current=%px\n",
+ de, de->d_parent, dir,
+ atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
inode_unlock(de->d_parent->d_inode);
dput(de);
}
@@ -4922,7 +4927,9 @@ static struct dentry *filename_create(int dfd, struct filename *name,
dentry = start_dirop(path->dentry, &last, reval_flag | create_flags);
if (IS_ERR(dentry))
goto out_drop_write;
-
+ pr_warn("DEBUG: after start_dirop: dentry=%px parent=%px parent_inode=%px rwsem owner=%px current=%px\n",
+ dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(dentry->d_parent)->i_rwsem.count), current);
if (unlikely(error))
goto fail;
@@ -4959,7 +4966,10 @@ EXPORT_SYMBOL(start_creating_path);
*/
void end_creating_path(const struct path *path, struct dentry *dentry)
{
- end_creating(dentry);
+ if (!IS_ERR(dentry)) {
+ inode_unlock(d_inode(path->dentry));
+ dput(dentry);
+ }
mnt_drop_write(path->mnt);
path_put(path);
}
@@ -5639,6 +5649,10 @@ int filename_symlinkat(struct filename *from, int newdfd, struct filename *to)
if (!error)
error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, from->name, &delegated_inode);
+ pr_warn("DEBUG: after vfs_symlink: error=%d dentry=%px parent=%px parent_inode=%px rwsem owner=%px path_dentry=%px path_inode=%px\n",
+ error, dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(path.dentry)->i_rwsem.count),
+ path.dentry, d_inode(path.dentry));
end_creating_path(&path, dentry);
if (is_delegated(&delegated_inode)) {
error = break_deleg_wait(&delegated_inode);
--
2.43.0
^ permalink raw reply related [flat|nested] 21+ messages in thread* Forwarded: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
2026-03-05 6:39 [syzbot] [exfat?] [gfs2?] WARNING in filename_symlinkat syzbot
2026-03-06 4:38 ` Forwarded: [PATCH] namei: fix parent inode unlock in end_creating_path() syzbot
2026-03-06 5:22 ` Forwarded: [PATCH] namei: add debug printk to trace parent inode lock state syzbot
@ 2026-03-06 6:25 ` syzbot
2026-03-06 7:51 ` syzbot
` (6 subsequent siblings)
9 siblings, 0 replies; 21+ messages in thread
From: syzbot @ 2026-03-06 6:25 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Add a debug printk when gfs2_dir_search finds an existing entry in
gfs2_create_inode. This helps confirm whether the rwsem unlock WARNING
in filename_symlinkat is caused by gfs2_create_inode returning false
success (0) when file is NULL and an existing entry is found on a
corrupted GFS2 image.
The printk logs the directory inode, creation mode, file pointer, found
inode, and rwsem owner at the point where the existing entry is
detected.
This is a temporary diagnostic patch and should be reverted once the
root cause is confirmed.
Reported-by: syzbot+2ed46b6b748df855347f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2ed46b6b748df855347f
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
---
fs/gfs2/inode.c | 3 +++
fs/namei.c | 18 ++++++++++++++++--
2 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 8344040ecaf7..e38dafea198c 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -738,6 +738,9 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
inode = gfs2_dir_search(dir, &dentry->d_name, !S_ISREG(mode) || excl);
error = PTR_ERR(inode);
if (!IS_ERR(inode)) {
+ pr_warn("DEBUG GFS2: gfs2_create_inode found existing entry! dir=%px mode=%o file=%px inode=%px S_ISDIR=%d rwsem owner=%px current=%px\n",
+ dir, mode, file, inode, S_ISDIR(inode->i_mode),
+ READ_ONCE(dir->i_rwsem.owner), current);
if (S_ISDIR(inode->i_mode)) {
iput(inode);
inode = NULL;
diff --git a/fs/namei.c b/fs/namei.c
index 58f715f7657e..9584ff6dff47 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2944,6 +2944,11 @@ struct dentry *start_dirop(struct dentry *parent, struct qstr *name,
void end_dirop(struct dentry *de)
{
if (!IS_ERR(de)) {
+ struct inode *dir = d_inode(de->d_parent);
+ pr_warn("DEBUG: end_dirop: de=%px parent=%px inode=%px rwsem count=%ld owner=%px current=%px\n",
+ de, de->d_parent, dir,
+ atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
inode_unlock(de->d_parent->d_inode);
dput(de);
}
@@ -4922,7 +4927,9 @@ static struct dentry *filename_create(int dfd, struct filename *name,
dentry = start_dirop(path->dentry, &last, reval_flag | create_flags);
if (IS_ERR(dentry))
goto out_drop_write;
-
+ pr_warn("DEBUG: after start_dirop: dentry=%px parent=%px parent_inode=%px rwsem owner=%px current=%px\n",
+ dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(dentry->d_parent)->i_rwsem.count), current);
if (unlikely(error))
goto fail;
@@ -4959,7 +4966,10 @@ EXPORT_SYMBOL(start_creating_path);
*/
void end_creating_path(const struct path *path, struct dentry *dentry)
{
- end_creating(dentry);
+ if (!IS_ERR(dentry)) {
+ inode_unlock(d_inode(path->dentry));
+ dput(dentry);
+ }
mnt_drop_write(path->mnt);
path_put(path);
}
@@ -5639,6 +5649,10 @@ int filename_symlinkat(struct filename *from, int newdfd, struct filename *to)
if (!error)
error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, from->name, &delegated_inode);
+ pr_warn("DEBUG: after vfs_symlink: error=%d dentry=%px parent=%px parent_inode=%px rwsem owner=%px path_dentry=%px path_inode=%px\n",
+ error, dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(path.dentry)->i_rwsem.count),
+ path.dentry, d_inode(path.dentry));
end_creating_path(&path, dentry);
if (is_delegated(&delegated_inode)) {
error = break_deleg_wait(&delegated_inode);
--
2.43.0
^ permalink raw reply related [flat|nested] 21+ messages in thread* Forwarded: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
2026-03-05 6:39 [syzbot] [exfat?] [gfs2?] WARNING in filename_symlinkat syzbot
` (2 preceding siblings ...)
2026-03-06 6:25 ` Forwarded: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode syzbot
@ 2026-03-06 7:51 ` syzbot
2026-03-06 8:25 ` syzbot
` (5 subsequent siblings)
9 siblings, 0 replies; 21+ messages in thread
From: syzbot @ 2026-03-06 7:51 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Add a debug printk when gfs2_dir_search finds an existing entry in
gfs2_create_inode. This helps confirm whether the rwsem unlock WARNING
in filename_symlinkat is caused by gfs2_create_inode returning false
success (0) when file is NULL and an existing entry is found on a
corrupted GFS2 image.
The printk logs the directory inode, creation mode, file pointer, found
inode, and rwsem owner at the point where the existing entry is
detected.
This is a temporary diagnostic patch and should be reverted once the
root cause is confirmed.
Reported-by: syzbot+2ed46b6b748df855347f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2ed46b6b748df855347f
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
---
fs/gfs2/inode.c | 3 +++
fs/namei.c | 24 ++++++++++++++++++++++--
2 files changed, 25 insertions(+), 2 deletions(-)
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 8344040ecaf7..e38dafea198c 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -738,6 +738,9 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
inode = gfs2_dir_search(dir, &dentry->d_name, !S_ISREG(mode) || excl);
error = PTR_ERR(inode);
if (!IS_ERR(inode)) {
+ pr_warn("DEBUG GFS2: gfs2_create_inode found existing entry! dir=%px mode=%o file=%px inode=%px S_ISDIR=%d rwsem owner=%px current=%px\n",
+ dir, mode, file, inode, S_ISDIR(inode->i_mode),
+ READ_ONCE(dir->i_rwsem.owner), current);
if (S_ISDIR(inode->i_mode)) {
iput(inode);
inode = NULL;
diff --git a/fs/namei.c b/fs/namei.c
index 58f715f7657e..caa2bf7c3401 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2944,6 +2944,11 @@ struct dentry *start_dirop(struct dentry *parent, struct qstr *name,
void end_dirop(struct dentry *de)
{
if (!IS_ERR(de)) {
+ struct inode *dir = d_inode(de->d_parent);
+ pr_warn("DEBUG: end_dirop: de=%px parent=%px inode=%px rwsem count=%ld owner=%px current=%px\n",
+ de, de->d_parent, dir,
+ atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
inode_unlock(de->d_parent->d_inode);
dput(de);
}
@@ -4922,7 +4927,9 @@ static struct dentry *filename_create(int dfd, struct filename *name,
dentry = start_dirop(path->dentry, &last, reval_flag | create_flags);
if (IS_ERR(dentry))
goto out_drop_write;
-
+ pr_warn("DEBUG: after start_dirop: dentry=%px parent=%px parent_inode=%px rwsem owner=%px current=%px\n",
+ dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(dentry->d_parent)->i_rwsem.count), current);
if (unlikely(error))
goto fail;
@@ -4959,7 +4966,10 @@ EXPORT_SYMBOL(start_creating_path);
*/
void end_creating_path(const struct path *path, struct dentry *dentry)
{
- end_creating(dentry);
+ if (!IS_ERR(dentry)) {
+ inode_unlock(d_inode(path->dentry));
+ dput(dentry);
+ }
mnt_drop_write(path->mnt);
path_put(path);
}
@@ -5595,6 +5605,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, const char *oldname,
struct delegated_inode *delegated_inode)
{
+ pr_warn("DEBUG VFS: before symlink: dir=%px sb_type=%s symlink_fn=%ps rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, dir->i_op->symlink,
+ READ_ONCE(dir->i_rwsem.owner), current);
int error;
error = may_create_dentry(idmap, dir, dentry);
@@ -5613,6 +5626,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
return error;
error = dir->i_op->symlink(idmap, dir, dentry, oldname);
+ pr_warn("DEBUG VFS: after symlink: dir=%px sb_type=%s error=%d rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, error,
+ READ_ONCE(dir->i_rwsem.owner), current);
if (!error)
fsnotify_create(dir, dentry);
return error;
@@ -5639,6 +5655,10 @@ int filename_symlinkat(struct filename *from, int newdfd, struct filename *to)
if (!error)
error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, from->name, &delegated_inode);
+ pr_warn("DEBUG: after vfs_symlink: error=%d dentry=%px parent=%px parent_inode=%px rwsem owner=%px path_dentry=%px path_inode=%px\n",
+ error, dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(path.dentry)->i_rwsem.count),
+ path.dentry, d_inode(path.dentry));
end_creating_path(&path, dentry);
if (is_delegated(&delegated_inode)) {
error = break_deleg_wait(&delegated_inode);
--
2.43.0
^ permalink raw reply related [flat|nested] 21+ messages in thread* Forwarded: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
2026-03-05 6:39 [syzbot] [exfat?] [gfs2?] WARNING in filename_symlinkat syzbot
` (3 preceding siblings ...)
2026-03-06 7:51 ` syzbot
@ 2026-03-06 8:25 ` syzbot
2026-03-06 9:16 ` syzbot
` (4 subsequent siblings)
9 siblings, 0 replies; 21+ messages in thread
From: syzbot @ 2026-03-06 8:25 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Add a debug printk when gfs2_dir_search finds an existing entry in
gfs2_create_inode. This helps confirm whether the rwsem unlock WARNING
in filename_symlinkat is caused by gfs2_create_inode returning false
success (0) when file is NULL and an existing entry is found on a
corrupted GFS2 image.
The printk logs the directory inode, creation mode, file pointer, found
inode, and rwsem owner at the point where the existing entry is
detected.
This is a temporary diagnostic patch and should be reverted once the
root cause is confirmed.
Reported-by: syzbot+2ed46b6b748df855347f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2ed46b6b748df855347f
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
---
fs/gfs2/inode.c | 3 +++
fs/namei.c | 30 ++++++++++++++++++++++++++++--
2 files changed, 31 insertions(+), 2 deletions(-)
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 8344040ecaf7..e38dafea198c 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -738,6 +738,9 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
inode = gfs2_dir_search(dir, &dentry->d_name, !S_ISREG(mode) || excl);
error = PTR_ERR(inode);
if (!IS_ERR(inode)) {
+ pr_warn("DEBUG GFS2: gfs2_create_inode found existing entry! dir=%px mode=%o file=%px inode=%px S_ISDIR=%d rwsem owner=%px current=%px\n",
+ dir, mode, file, inode, S_ISDIR(inode->i_mode),
+ READ_ONCE(dir->i_rwsem.owner), current);
if (S_ISDIR(inode->i_mode)) {
iput(inode);
inode = NULL;
diff --git a/fs/namei.c b/fs/namei.c
index 58f715f7657e..768944691e24 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2922,7 +2922,13 @@ static struct dentry *__start_dirop(struct dentry *parent, struct qstr *name,
} else {
inode_lock_nested(dir, I_MUTEX_PARENT);
}
+ pr_warn("DEBUG LOCK: __start_dirop locked dir=%px count=%ld owner=%px current=%px\n",
+ dir, atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
dentry = lookup_one_qstr_excl(name, parent, lookup_flags);
+ pr_warn("DEBUG LOCK: __start_dirop after lookup dir=%px count=%ld owner=%px current=%px dentry_err=%d\n",
+ dir, atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current, IS_ERR(dentry));
if (IS_ERR(dentry))
inode_unlock(dir);
return dentry;
@@ -2944,6 +2950,11 @@ struct dentry *start_dirop(struct dentry *parent, struct qstr *name,
void end_dirop(struct dentry *de)
{
if (!IS_ERR(de)) {
+ struct inode *dir = d_inode(de->d_parent);
+ pr_warn("DEBUG: end_dirop: de=%px parent=%px inode=%px rwsem count=%ld owner=%px current=%px\n",
+ de, de->d_parent, dir,
+ atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
inode_unlock(de->d_parent->d_inode);
dput(de);
}
@@ -4922,7 +4933,9 @@ static struct dentry *filename_create(int dfd, struct filename *name,
dentry = start_dirop(path->dentry, &last, reval_flag | create_flags);
if (IS_ERR(dentry))
goto out_drop_write;
-
+ pr_warn("DEBUG: after start_dirop: dentry=%px parent=%px parent_inode=%px rwsem owner=%px current=%px\n",
+ dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(dentry->d_parent)->i_rwsem.count), current);
if (unlikely(error))
goto fail;
@@ -4959,7 +4972,10 @@ EXPORT_SYMBOL(start_creating_path);
*/
void end_creating_path(const struct path *path, struct dentry *dentry)
{
- end_creating(dentry);
+ if (!IS_ERR(dentry)) {
+ inode_unlock(d_inode(path->dentry));
+ dput(dentry);
+ }
mnt_drop_write(path->mnt);
path_put(path);
}
@@ -5595,6 +5611,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, const char *oldname,
struct delegated_inode *delegated_inode)
{
+ pr_warn("DEBUG VFS: before symlink: dir=%px sb_type=%s symlink_fn=%ps rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, dir->i_op->symlink,
+ READ_ONCE(dir->i_rwsem.owner), current);
int error;
error = may_create_dentry(idmap, dir, dentry);
@@ -5613,6 +5632,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
return error;
error = dir->i_op->symlink(idmap, dir, dentry, oldname);
+ pr_warn("DEBUG VFS: after symlink: dir=%px sb_type=%s error=%d rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, error,
+ READ_ONCE(dir->i_rwsem.owner), current);
if (!error)
fsnotify_create(dir, dentry);
return error;
@@ -5639,6 +5661,10 @@ int filename_symlinkat(struct filename *from, int newdfd, struct filename *to)
if (!error)
error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, from->name, &delegated_inode);
+ pr_warn("DEBUG: after vfs_symlink: error=%d dentry=%px parent=%px parent_inode=%px rwsem owner=%px path_dentry=%px path_inode=%px\n",
+ error, dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(path.dentry)->i_rwsem.count),
+ path.dentry, d_inode(path.dentry));
end_creating_path(&path, dentry);
if (is_delegated(&delegated_inode)) {
error = break_deleg_wait(&delegated_inode);
--
2.43.0
^ permalink raw reply related [flat|nested] 21+ messages in thread* Forwarded: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
2026-03-05 6:39 [syzbot] [exfat?] [gfs2?] WARNING in filename_symlinkat syzbot
` (4 preceding siblings ...)
2026-03-06 8:25 ` syzbot
@ 2026-03-06 9:16 ` syzbot
2026-03-06 9:57 ` syzbot
` (3 subsequent siblings)
9 siblings, 0 replies; 21+ messages in thread
From: syzbot @ 2026-03-06 9:16 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Add a debug printk when gfs2_dir_search finds an existing entry in
gfs2_create_inode. This helps confirm whether the rwsem unlock WARNING
in filename_symlinkat is caused by gfs2_create_inode returning false
success (0) when file is NULL and an existing entry is found on a
corrupted GFS2 image.
The printk logs the directory inode, creation mode, file pointer, found
inode, and rwsem owner at the point where the existing entry is
detected.
This is a temporary diagnostic patch and should be reverted once the
root cause is confirmed.
Reported-by: syzbot+2ed46b6b748df855347f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2ed46b6b748df855347f
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
---
fs/gfs2/inode.c | 13 +++++++++++++
fs/namei.c | 30 ++++++++++++++++++++++++++++--
2 files changed, 41 insertions(+), 2 deletions(-)
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 8344040ecaf7..9a3df067bea6 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -725,6 +725,8 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = gfs2_rindex_update(sdp);
if (error)
goto fail;
+ pr_warn("DEBUG GFS2: after glock_nq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
error = gfs2_glock_nq_init(dip->i_gl, LM_ST_EXCLUSIVE, 0, &d_gh);
if (error)
@@ -738,6 +740,9 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
inode = gfs2_dir_search(dir, &dentry->d_name, !S_ISREG(mode) || excl);
error = PTR_ERR(inode);
if (!IS_ERR(inode)) {
+ pr_warn("DEBUG GFS2: gfs2_create_inode found existing entry! dir=%px mode=%o file=%px inode=%px S_ISDIR=%d rwsem owner=%px current=%px\n",
+ dir, mode, file, inode, S_ISDIR(inode->i_mode),
+ READ_ONCE(dir->i_rwsem.owner), current);
if (S_ISDIR(inode->i_mode)) {
iput(inode);
inode = NULL;
@@ -893,6 +898,8 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
mark_inode_dirty(inode);
d_instantiate(dentry, inode);
+ pr_warn("DEBUG GFS2: before glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
/* After instantiate, errors should result in evict which will destroy
* both inode and iopen glocks properly. */
if (file) {
@@ -900,6 +907,8 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = finish_open(file, dentry, gfs2_open_common);
}
gfs2_glock_dq_uninit(&d_gh);
+ pr_warn("DEBUG GFS2: after glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
gfs2_qa_put(ip);
gfs2_glock_dq_uninit(&gh);
gfs2_glock_put(io_gl);
@@ -937,7 +946,11 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
posix_acl_release(acl);
fail_gunlock:
gfs2_dir_no_add(&da);
+ pr_warn("DEBUG GFS2: fail_gunlock before glock_dq dir=%px rwsem owner=%px current=%px error=%d\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current, error);
gfs2_glock_dq_uninit(&d_gh);
+ pr_warn("DEBUG GFS2: fail_gunlock after glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
if (!IS_ERR_OR_NULL(inode)) {
if (inode_state_read_once(inode) & I_NEW)
iget_failed(inode);
diff --git a/fs/namei.c b/fs/namei.c
index 58f715f7657e..768944691e24 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2922,7 +2922,13 @@ static struct dentry *__start_dirop(struct dentry *parent, struct qstr *name,
} else {
inode_lock_nested(dir, I_MUTEX_PARENT);
}
+ pr_warn("DEBUG LOCK: __start_dirop locked dir=%px count=%ld owner=%px current=%px\n",
+ dir, atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
dentry = lookup_one_qstr_excl(name, parent, lookup_flags);
+ pr_warn("DEBUG LOCK: __start_dirop after lookup dir=%px count=%ld owner=%px current=%px dentry_err=%d\n",
+ dir, atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current, IS_ERR(dentry));
if (IS_ERR(dentry))
inode_unlock(dir);
return dentry;
@@ -2944,6 +2950,11 @@ struct dentry *start_dirop(struct dentry *parent, struct qstr *name,
void end_dirop(struct dentry *de)
{
if (!IS_ERR(de)) {
+ struct inode *dir = d_inode(de->d_parent);
+ pr_warn("DEBUG: end_dirop: de=%px parent=%px inode=%px rwsem count=%ld owner=%px current=%px\n",
+ de, de->d_parent, dir,
+ atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
inode_unlock(de->d_parent->d_inode);
dput(de);
}
@@ -4922,7 +4933,9 @@ static struct dentry *filename_create(int dfd, struct filename *name,
dentry = start_dirop(path->dentry, &last, reval_flag | create_flags);
if (IS_ERR(dentry))
goto out_drop_write;
-
+ pr_warn("DEBUG: after start_dirop: dentry=%px parent=%px parent_inode=%px rwsem owner=%px current=%px\n",
+ dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(dentry->d_parent)->i_rwsem.count), current);
if (unlikely(error))
goto fail;
@@ -4959,7 +4972,10 @@ EXPORT_SYMBOL(start_creating_path);
*/
void end_creating_path(const struct path *path, struct dentry *dentry)
{
- end_creating(dentry);
+ if (!IS_ERR(dentry)) {
+ inode_unlock(d_inode(path->dentry));
+ dput(dentry);
+ }
mnt_drop_write(path->mnt);
path_put(path);
}
@@ -5595,6 +5611,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, const char *oldname,
struct delegated_inode *delegated_inode)
{
+ pr_warn("DEBUG VFS: before symlink: dir=%px sb_type=%s symlink_fn=%ps rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, dir->i_op->symlink,
+ READ_ONCE(dir->i_rwsem.owner), current);
int error;
error = may_create_dentry(idmap, dir, dentry);
@@ -5613,6 +5632,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
return error;
error = dir->i_op->symlink(idmap, dir, dentry, oldname);
+ pr_warn("DEBUG VFS: after symlink: dir=%px sb_type=%s error=%d rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, error,
+ READ_ONCE(dir->i_rwsem.owner), current);
if (!error)
fsnotify_create(dir, dentry);
return error;
@@ -5639,6 +5661,10 @@ int filename_symlinkat(struct filename *from, int newdfd, struct filename *to)
if (!error)
error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, from->name, &delegated_inode);
+ pr_warn("DEBUG: after vfs_symlink: error=%d dentry=%px parent=%px parent_inode=%px rwsem owner=%px path_dentry=%px path_inode=%px\n",
+ error, dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(path.dentry)->i_rwsem.count),
+ path.dentry, d_inode(path.dentry));
end_creating_path(&path, dentry);
if (is_delegated(&delegated_inode)) {
error = break_deleg_wait(&delegated_inode);
--
2.43.0
^ permalink raw reply related [flat|nested] 21+ messages in thread* Forwarded: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
2026-03-05 6:39 [syzbot] [exfat?] [gfs2?] WARNING in filename_symlinkat syzbot
` (5 preceding siblings ...)
2026-03-06 9:16 ` syzbot
@ 2026-03-06 9:57 ` syzbot
2026-03-06 10:41 ` syzbot
` (2 subsequent siblings)
9 siblings, 0 replies; 21+ messages in thread
From: syzbot @ 2026-03-06 9:57 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Add a debug printk when gfs2_dir_search finds an existing entry in
gfs2_create_inode. This helps confirm whether the rwsem unlock WARNING
in filename_symlinkat is caused by gfs2_create_inode returning false
success (0) when file is NULL and an existing entry is found on a
corrupted GFS2 image.
The printk logs the directory inode, creation mode, file pointer, found
inode, and rwsem owner at the point where the existing entry is
detected.
This is a temporary diagnostic patch and should be reverted once the
root cause is confirmed.
Reported-by: syzbot+2ed46b6b748df855347f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2ed46b6b748df855347f
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
---
fs/gfs2/inode.c | 22 +++++++++++++++++++++-
fs/namei.c | 30 ++++++++++++++++++++++++++++--
2 files changed, 49 insertions(+), 3 deletions(-)
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 8344040ecaf7..a393d72597b8 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -725,19 +725,26 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = gfs2_rindex_update(sdp);
if (error)
goto fail;
+ pr_warn("DEBUG GFS2: after glock_nq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
error = gfs2_glock_nq_init(dip->i_gl, LM_ST_EXCLUSIVE, 0, &d_gh);
+ pr_warn("DEBUG GFS2 A: dir=%px rwsem owner=%px\n", dir, READ_ONCE(dir->i_rwsem.owner));
if (error)
goto fail;
gfs2_holder_mark_uninitialized(&gh);
error = create_ok(dip, name, mode);
+ pr_warn("DEBUG GFS2 B: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_gunlock;
inode = gfs2_dir_search(dir, &dentry->d_name, !S_ISREG(mode) || excl);
error = PTR_ERR(inode);
if (!IS_ERR(inode)) {
+ pr_warn("DEBUG GFS2: gfs2_create_inode found existing entry! dir=%px mode=%o file=%px inode=%px S_ISDIR=%d rwsem owner=%px current=%px\n",
+ dir, mode, file, inode, S_ISDIR(inode->i_mode),
+ READ_ONCE(dir->i_rwsem.owner), current);
if (S_ISDIR(inode->i_mode)) {
iput(inode);
inode = NULL;
@@ -759,6 +766,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
}
error = gfs2_diradd_alloc_required(dir, name, &da);
+ pr_warn("DEBUG GFS2 C: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error < 0)
goto fail_gunlock;
@@ -820,6 +828,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
blocks++;
error = alloc_dinode(ip, aflags, &blocks);
+ pr_warn("DEBUG GFS2 D: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_free_inode;
@@ -844,6 +853,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = gfs2_glock_nq_init(io_gl, LM_ST_SHARED, GL_EXACT | GL_NOPID,
&ip->i_iopen_gh);
+ pr_warn("DEBUG GFS2 E: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_gunlock2;
@@ -862,7 +872,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
}
init_dinode(dip, ip, symname);
gfs2_trans_end(sdp);
-
+ pr_warn("DEBUG GFS2 F: dir=%px rwsem owner=%px\n", dir, READ_ONCE(dir->i_rwsem.owner));
glock_set_object(ip->i_gl, ip);
glock_set_object(io_gl, ip);
gfs2_set_iop(inode);
@@ -888,11 +898,15 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
goto fail_gunlock4;
error = link_dinode(dip, name, ip, &da);
+ pr_warn("DEBUG GFS2 G: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_gunlock4;
mark_inode_dirty(inode);
d_instantiate(dentry, inode);
+ pr_warn("DEBUG GFS2 H: dir=%px rwsem owner=%px\n", dir, READ_ONCE(dir->i_rwsem.owner));
+ pr_warn("DEBUG GFS2: before glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
/* After instantiate, errors should result in evict which will destroy
* both inode and iopen glocks properly. */
if (file) {
@@ -900,6 +914,8 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = finish_open(file, dentry, gfs2_open_common);
}
gfs2_glock_dq_uninit(&d_gh);
+ pr_warn("DEBUG GFS2: after glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
gfs2_qa_put(ip);
gfs2_glock_dq_uninit(&gh);
gfs2_glock_put(io_gl);
@@ -937,7 +953,11 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
posix_acl_release(acl);
fail_gunlock:
gfs2_dir_no_add(&da);
+ pr_warn("DEBUG GFS2: fail_gunlock before glock_dq dir=%px rwsem owner=%px current=%px error=%d\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current, error);
gfs2_glock_dq_uninit(&d_gh);
+ pr_warn("DEBUG GFS2: fail_gunlock after glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
if (!IS_ERR_OR_NULL(inode)) {
if (inode_state_read_once(inode) & I_NEW)
iget_failed(inode);
diff --git a/fs/namei.c b/fs/namei.c
index 58f715f7657e..768944691e24 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2922,7 +2922,13 @@ static struct dentry *__start_dirop(struct dentry *parent, struct qstr *name,
} else {
inode_lock_nested(dir, I_MUTEX_PARENT);
}
+ pr_warn("DEBUG LOCK: __start_dirop locked dir=%px count=%ld owner=%px current=%px\n",
+ dir, atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
dentry = lookup_one_qstr_excl(name, parent, lookup_flags);
+ pr_warn("DEBUG LOCK: __start_dirop after lookup dir=%px count=%ld owner=%px current=%px dentry_err=%d\n",
+ dir, atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current, IS_ERR(dentry));
if (IS_ERR(dentry))
inode_unlock(dir);
return dentry;
@@ -2944,6 +2950,11 @@ struct dentry *start_dirop(struct dentry *parent, struct qstr *name,
void end_dirop(struct dentry *de)
{
if (!IS_ERR(de)) {
+ struct inode *dir = d_inode(de->d_parent);
+ pr_warn("DEBUG: end_dirop: de=%px parent=%px inode=%px rwsem count=%ld owner=%px current=%px\n",
+ de, de->d_parent, dir,
+ atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
inode_unlock(de->d_parent->d_inode);
dput(de);
}
@@ -4922,7 +4933,9 @@ static struct dentry *filename_create(int dfd, struct filename *name,
dentry = start_dirop(path->dentry, &last, reval_flag | create_flags);
if (IS_ERR(dentry))
goto out_drop_write;
-
+ pr_warn("DEBUG: after start_dirop: dentry=%px parent=%px parent_inode=%px rwsem owner=%px current=%px\n",
+ dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(dentry->d_parent)->i_rwsem.count), current);
if (unlikely(error))
goto fail;
@@ -4959,7 +4972,10 @@ EXPORT_SYMBOL(start_creating_path);
*/
void end_creating_path(const struct path *path, struct dentry *dentry)
{
- end_creating(dentry);
+ if (!IS_ERR(dentry)) {
+ inode_unlock(d_inode(path->dentry));
+ dput(dentry);
+ }
mnt_drop_write(path->mnt);
path_put(path);
}
@@ -5595,6 +5611,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, const char *oldname,
struct delegated_inode *delegated_inode)
{
+ pr_warn("DEBUG VFS: before symlink: dir=%px sb_type=%s symlink_fn=%ps rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, dir->i_op->symlink,
+ READ_ONCE(dir->i_rwsem.owner), current);
int error;
error = may_create_dentry(idmap, dir, dentry);
@@ -5613,6 +5632,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
return error;
error = dir->i_op->symlink(idmap, dir, dentry, oldname);
+ pr_warn("DEBUG VFS: after symlink: dir=%px sb_type=%s error=%d rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, error,
+ READ_ONCE(dir->i_rwsem.owner), current);
if (!error)
fsnotify_create(dir, dentry);
return error;
@@ -5639,6 +5661,10 @@ int filename_symlinkat(struct filename *from, int newdfd, struct filename *to)
if (!error)
error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, from->name, &delegated_inode);
+ pr_warn("DEBUG: after vfs_symlink: error=%d dentry=%px parent=%px parent_inode=%px rwsem owner=%px path_dentry=%px path_inode=%px\n",
+ error, dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(path.dentry)->i_rwsem.count),
+ path.dentry, d_inode(path.dentry));
end_creating_path(&path, dentry);
if (is_delegated(&delegated_inode)) {
error = break_deleg_wait(&delegated_inode);
--
2.43.0
^ permalink raw reply related [flat|nested] 21+ messages in thread* Forwarded: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
2026-03-05 6:39 [syzbot] [exfat?] [gfs2?] WARNING in filename_symlinkat syzbot
` (6 preceding siblings ...)
2026-03-06 9:57 ` syzbot
@ 2026-03-06 10:41 ` syzbot
2026-03-06 12:38 ` syzbot
2026-03-06 13:12 ` syzbot
9 siblings, 0 replies; 21+ messages in thread
From: syzbot @ 2026-03-06 10:41 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Add a debug printk when gfs2_dir_search finds an existing entry in
gfs2_create_inode. This helps confirm whether the rwsem unlock WARNING
in filename_symlinkat is caused by gfs2_create_inode returning false
success (0) when file is NULL and an existing entry is found on a
corrupted GFS2 image.
The printk logs the directory inode, creation mode, file pointer, found
inode, and rwsem owner at the point where the existing entry is
detected.
This is a temporary diagnostic patch and should be reverted once the
root cause is confirmed.
Reported-by: syzbot+2ed46b6b748df855347f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2ed46b6b748df855347f
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
---
fs/gfs2/inode.c | 26 +++++++++++++++++++++++++-
fs/namei.c | 30 ++++++++++++++++++++++++++++--
2 files changed, 53 insertions(+), 3 deletions(-)
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 8344040ecaf7..e252f7720735 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -725,19 +725,26 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = gfs2_rindex_update(sdp);
if (error)
goto fail;
+ pr_warn("DEBUG GFS2: after glock_nq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
error = gfs2_glock_nq_init(dip->i_gl, LM_ST_EXCLUSIVE, 0, &d_gh);
+ pr_warn("DEBUG GFS2 A: dir=%px rwsem owner=%px\n", dir, READ_ONCE(dir->i_rwsem.owner));
if (error)
goto fail;
gfs2_holder_mark_uninitialized(&gh);
error = create_ok(dip, name, mode);
+ pr_warn("DEBUG GFS2 B: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_gunlock;
inode = gfs2_dir_search(dir, &dentry->d_name, !S_ISREG(mode) || excl);
error = PTR_ERR(inode);
if (!IS_ERR(inode)) {
+ pr_warn("DEBUG GFS2: gfs2_create_inode found existing entry! dir=%px mode=%o file=%px inode=%px S_ISDIR=%d rwsem owner=%px current=%px\n",
+ dir, mode, file, inode, S_ISDIR(inode->i_mode),
+ READ_ONCE(dir->i_rwsem.owner), current);
if (S_ISDIR(inode->i_mode)) {
iput(inode);
inode = NULL;
@@ -759,6 +766,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
}
error = gfs2_diradd_alloc_required(dir, name, &da);
+ pr_warn("DEBUG GFS2 C: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error < 0)
goto fail_gunlock;
@@ -820,16 +828,20 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
blocks++;
error = alloc_dinode(ip, aflags, &blocks);
+ pr_warn("DEBUG GFS2 D: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_free_inode;
gfs2_set_inode_blocks(inode, blocks);
error = gfs2_glock_get(sdp, ip->i_no_addr, &gfs2_inode_glops, CREATE, &ip->i_gl);
+ pr_warn("DEBUG GFS2 D1: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
+ if (error)
if (error)
goto fail_dealloc_inode;
error = gfs2_glock_get(sdp, ip->i_no_addr, &gfs2_iopen_glops, CREATE, &io_gl);
+ pr_warn("DEBUG GFS2 D2: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_dealloc_inode;
gfs2_cancel_delete_work(io_gl);
@@ -837,6 +849,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
retry:
error = insert_inode_locked4(inode, ip->i_no_addr, iget_test, &ip->i_no_addr);
+ pr_warn("DEBUG GFS2 D3: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error == -EBUSY)
goto retry;
if (error)
@@ -844,6 +857,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = gfs2_glock_nq_init(io_gl, LM_ST_SHARED, GL_EXACT | GL_NOPID,
&ip->i_iopen_gh);
+ pr_warn("DEBUG GFS2 E: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_gunlock2;
@@ -862,7 +876,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
}
init_dinode(dip, ip, symname);
gfs2_trans_end(sdp);
-
+ pr_warn("DEBUG GFS2 F: dir=%px rwsem owner=%px\n", dir, READ_ONCE(dir->i_rwsem.owner));
glock_set_object(ip->i_gl, ip);
glock_set_object(io_gl, ip);
gfs2_set_iop(inode);
@@ -888,11 +902,15 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
goto fail_gunlock4;
error = link_dinode(dip, name, ip, &da);
+ pr_warn("DEBUG GFS2 G: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_gunlock4;
mark_inode_dirty(inode);
d_instantiate(dentry, inode);
+ pr_warn("DEBUG GFS2 H: dir=%px rwsem owner=%px\n", dir, READ_ONCE(dir->i_rwsem.owner));
+ pr_warn("DEBUG GFS2: before glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
/* After instantiate, errors should result in evict which will destroy
* both inode and iopen glocks properly. */
if (file) {
@@ -900,6 +918,8 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = finish_open(file, dentry, gfs2_open_common);
}
gfs2_glock_dq_uninit(&d_gh);
+ pr_warn("DEBUG GFS2: after glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
gfs2_qa_put(ip);
gfs2_glock_dq_uninit(&gh);
gfs2_glock_put(io_gl);
@@ -937,7 +957,11 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
posix_acl_release(acl);
fail_gunlock:
gfs2_dir_no_add(&da);
+ pr_warn("DEBUG GFS2: fail_gunlock before glock_dq dir=%px rwsem owner=%px current=%px error=%d\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current, error);
gfs2_glock_dq_uninit(&d_gh);
+ pr_warn("DEBUG GFS2: fail_gunlock after glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
if (!IS_ERR_OR_NULL(inode)) {
if (inode_state_read_once(inode) & I_NEW)
iget_failed(inode);
diff --git a/fs/namei.c b/fs/namei.c
index 58f715f7657e..768944691e24 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2922,7 +2922,13 @@ static struct dentry *__start_dirop(struct dentry *parent, struct qstr *name,
} else {
inode_lock_nested(dir, I_MUTEX_PARENT);
}
+ pr_warn("DEBUG LOCK: __start_dirop locked dir=%px count=%ld owner=%px current=%px\n",
+ dir, atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
dentry = lookup_one_qstr_excl(name, parent, lookup_flags);
+ pr_warn("DEBUG LOCK: __start_dirop after lookup dir=%px count=%ld owner=%px current=%px dentry_err=%d\n",
+ dir, atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current, IS_ERR(dentry));
if (IS_ERR(dentry))
inode_unlock(dir);
return dentry;
@@ -2944,6 +2950,11 @@ struct dentry *start_dirop(struct dentry *parent, struct qstr *name,
void end_dirop(struct dentry *de)
{
if (!IS_ERR(de)) {
+ struct inode *dir = d_inode(de->d_parent);
+ pr_warn("DEBUG: end_dirop: de=%px parent=%px inode=%px rwsem count=%ld owner=%px current=%px\n",
+ de, de->d_parent, dir,
+ atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
inode_unlock(de->d_parent->d_inode);
dput(de);
}
@@ -4922,7 +4933,9 @@ static struct dentry *filename_create(int dfd, struct filename *name,
dentry = start_dirop(path->dentry, &last, reval_flag | create_flags);
if (IS_ERR(dentry))
goto out_drop_write;
-
+ pr_warn("DEBUG: after start_dirop: dentry=%px parent=%px parent_inode=%px rwsem owner=%px current=%px\n",
+ dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(dentry->d_parent)->i_rwsem.count), current);
if (unlikely(error))
goto fail;
@@ -4959,7 +4972,10 @@ EXPORT_SYMBOL(start_creating_path);
*/
void end_creating_path(const struct path *path, struct dentry *dentry)
{
- end_creating(dentry);
+ if (!IS_ERR(dentry)) {
+ inode_unlock(d_inode(path->dentry));
+ dput(dentry);
+ }
mnt_drop_write(path->mnt);
path_put(path);
}
@@ -5595,6 +5611,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, const char *oldname,
struct delegated_inode *delegated_inode)
{
+ pr_warn("DEBUG VFS: before symlink: dir=%px sb_type=%s symlink_fn=%ps rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, dir->i_op->symlink,
+ READ_ONCE(dir->i_rwsem.owner), current);
int error;
error = may_create_dentry(idmap, dir, dentry);
@@ -5613,6 +5632,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
return error;
error = dir->i_op->symlink(idmap, dir, dentry, oldname);
+ pr_warn("DEBUG VFS: after symlink: dir=%px sb_type=%s error=%d rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, error,
+ READ_ONCE(dir->i_rwsem.owner), current);
if (!error)
fsnotify_create(dir, dentry);
return error;
@@ -5639,6 +5661,10 @@ int filename_symlinkat(struct filename *from, int newdfd, struct filename *to)
if (!error)
error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, from->name, &delegated_inode);
+ pr_warn("DEBUG: after vfs_symlink: error=%d dentry=%px parent=%px parent_inode=%px rwsem owner=%px path_dentry=%px path_inode=%px\n",
+ error, dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(path.dentry)->i_rwsem.count),
+ path.dentry, d_inode(path.dentry));
end_creating_path(&path, dentry);
if (is_delegated(&delegated_inode)) {
error = break_deleg_wait(&delegated_inode);
--
2.43.0
^ permalink raw reply related [flat|nested] 21+ messages in thread* Forwarded: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
2026-03-05 6:39 [syzbot] [exfat?] [gfs2?] WARNING in filename_symlinkat syzbot
` (7 preceding siblings ...)
2026-03-06 10:41 ` syzbot
@ 2026-03-06 12:38 ` syzbot
2026-03-06 13:12 ` syzbot
9 siblings, 0 replies; 21+ messages in thread
From: syzbot @ 2026-03-06 12:38 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Add a debug printk when gfs2_dir_search finds an existing entry in
gfs2_create_inode. This helps confirm whether the rwsem unlock WARNING
in filename_symlinkat is caused by gfs2_create_inode returning false
success (0) when file is NULL and an existing entry is found on a
corrupted GFS2 image.
The printk logs the directory inode, creation mode, file pointer, found
inode, and rwsem owner at the point where the existing entry is
detected.
This is a temporary diagnostic patch and should be reverted once the
root cause is confirmed.
Reported-by: syzbot+2ed46b6b748df855347f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2ed46b6b748df855347f
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
---
fs/gfs2/inode.c | 30 +++++++++++++++++++++++++++++-
fs/namei.c | 30 ++++++++++++++++++++++++++++--
kernel/locking/rwsem.c | 10 ++++++++++
3 files changed, 67 insertions(+), 3 deletions(-)
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 8344040ecaf7..2be4a899c665 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -36,6 +36,9 @@
#include "super.h"
#include "glops.h"
+void *gfs2_debug_watched_rwsem;
+EXPORT_SYMBOL(gfs2_debug_watched_rwsem);
+
static const struct inode_operations gfs2_file_iops;
static const struct inode_operations gfs2_dir_iops;
static const struct inode_operations gfs2_symlink_iops;
@@ -725,19 +728,26 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = gfs2_rindex_update(sdp);
if (error)
goto fail;
+ pr_warn("DEBUG GFS2: after glock_nq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
error = gfs2_glock_nq_init(dip->i_gl, LM_ST_EXCLUSIVE, 0, &d_gh);
+ pr_warn("DEBUG GFS2 A: dir=%px rwsem owner=%px\n", dir, READ_ONCE(dir->i_rwsem.owner));
if (error)
goto fail;
gfs2_holder_mark_uninitialized(&gh);
error = create_ok(dip, name, mode);
+ pr_warn("DEBUG GFS2 B: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_gunlock;
inode = gfs2_dir_search(dir, &dentry->d_name, !S_ISREG(mode) || excl);
error = PTR_ERR(inode);
if (!IS_ERR(inode)) {
+ pr_warn("DEBUG GFS2: gfs2_create_inode found existing entry! dir=%px mode=%o file=%px inode=%px S_ISDIR=%d rwsem owner=%px current=%px\n",
+ dir, mode, file, inode, S_ISDIR(inode->i_mode),
+ READ_ONCE(dir->i_rwsem.owner), current);
if (S_ISDIR(inode->i_mode)) {
iput(inode);
inode = NULL;
@@ -759,6 +769,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
}
error = gfs2_diradd_alloc_required(dir, name, &da);
+ pr_warn("DEBUG GFS2 C: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error < 0)
goto fail_gunlock;
@@ -820,16 +831,19 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
blocks++;
error = alloc_dinode(ip, aflags, &blocks);
+ pr_warn("DEBUG GFS2 D: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_free_inode;
gfs2_set_inode_blocks(inode, blocks);
error = gfs2_glock_get(sdp, ip->i_no_addr, &gfs2_inode_glops, CREATE, &ip->i_gl);
+ pr_warn("DEBUG GFS2 D1: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_dealloc_inode;
error = gfs2_glock_get(sdp, ip->i_no_addr, &gfs2_iopen_glops, CREATE, &io_gl);
+ pr_warn("DEBUG GFS2 D2: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_dealloc_inode;
gfs2_cancel_delete_work(io_gl);
@@ -837,13 +851,17 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
retry:
error = insert_inode_locked4(inode, ip->i_no_addr, iget_test, &ip->i_no_addr);
+ pr_warn("DEBUG GFS2 D3: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error == -EBUSY)
goto retry;
if (error)
goto fail_gunlock2;
+ gfs2_debug_watched_rwsem = &dir->i_rwsem;
error = gfs2_glock_nq_init(io_gl, LM_ST_SHARED, GL_EXACT | GL_NOPID,
&ip->i_iopen_gh);
+ gfs2_debug_watched_rwsem = NULL;
+ pr_warn("DEBUG GFS2 E: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_gunlock2;
@@ -862,7 +880,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
}
init_dinode(dip, ip, symname);
gfs2_trans_end(sdp);
-
+ pr_warn("DEBUG GFS2 F: dir=%px rwsem owner=%px\n", dir, READ_ONCE(dir->i_rwsem.owner));
glock_set_object(ip->i_gl, ip);
glock_set_object(io_gl, ip);
gfs2_set_iop(inode);
@@ -888,11 +906,15 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
goto fail_gunlock4;
error = link_dinode(dip, name, ip, &da);
+ pr_warn("DEBUG GFS2 G: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_gunlock4;
mark_inode_dirty(inode);
d_instantiate(dentry, inode);
+ pr_warn("DEBUG GFS2 H: dir=%px rwsem owner=%px\n", dir, READ_ONCE(dir->i_rwsem.owner));
+ pr_warn("DEBUG GFS2: before glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
/* After instantiate, errors should result in evict which will destroy
* both inode and iopen glocks properly. */
if (file) {
@@ -900,6 +922,8 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = finish_open(file, dentry, gfs2_open_common);
}
gfs2_glock_dq_uninit(&d_gh);
+ pr_warn("DEBUG GFS2: after glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
gfs2_qa_put(ip);
gfs2_glock_dq_uninit(&gh);
gfs2_glock_put(io_gl);
@@ -937,7 +961,11 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
posix_acl_release(acl);
fail_gunlock:
gfs2_dir_no_add(&da);
+ pr_warn("DEBUG GFS2: fail_gunlock before glock_dq dir=%px rwsem owner=%px current=%px error=%d\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current, error);
gfs2_glock_dq_uninit(&d_gh);
+ pr_warn("DEBUG GFS2: fail_gunlock after glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
if (!IS_ERR_OR_NULL(inode)) {
if (inode_state_read_once(inode) & I_NEW)
iget_failed(inode);
diff --git a/fs/namei.c b/fs/namei.c
index 58f715f7657e..768944691e24 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2922,7 +2922,13 @@ static struct dentry *__start_dirop(struct dentry *parent, struct qstr *name,
} else {
inode_lock_nested(dir, I_MUTEX_PARENT);
}
+ pr_warn("DEBUG LOCK: __start_dirop locked dir=%px count=%ld owner=%px current=%px\n",
+ dir, atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
dentry = lookup_one_qstr_excl(name, parent, lookup_flags);
+ pr_warn("DEBUG LOCK: __start_dirop after lookup dir=%px count=%ld owner=%px current=%px dentry_err=%d\n",
+ dir, atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current, IS_ERR(dentry));
if (IS_ERR(dentry))
inode_unlock(dir);
return dentry;
@@ -2944,6 +2950,11 @@ struct dentry *start_dirop(struct dentry *parent, struct qstr *name,
void end_dirop(struct dentry *de)
{
if (!IS_ERR(de)) {
+ struct inode *dir = d_inode(de->d_parent);
+ pr_warn("DEBUG: end_dirop: de=%px parent=%px inode=%px rwsem count=%ld owner=%px current=%px\n",
+ de, de->d_parent, dir,
+ atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
inode_unlock(de->d_parent->d_inode);
dput(de);
}
@@ -4922,7 +4933,9 @@ static struct dentry *filename_create(int dfd, struct filename *name,
dentry = start_dirop(path->dentry, &last, reval_flag | create_flags);
if (IS_ERR(dentry))
goto out_drop_write;
-
+ pr_warn("DEBUG: after start_dirop: dentry=%px parent=%px parent_inode=%px rwsem owner=%px current=%px\n",
+ dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(dentry->d_parent)->i_rwsem.count), current);
if (unlikely(error))
goto fail;
@@ -4959,7 +4972,10 @@ EXPORT_SYMBOL(start_creating_path);
*/
void end_creating_path(const struct path *path, struct dentry *dentry)
{
- end_creating(dentry);
+ if (!IS_ERR(dentry)) {
+ inode_unlock(d_inode(path->dentry));
+ dput(dentry);
+ }
mnt_drop_write(path->mnt);
path_put(path);
}
@@ -5595,6 +5611,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, const char *oldname,
struct delegated_inode *delegated_inode)
{
+ pr_warn("DEBUG VFS: before symlink: dir=%px sb_type=%s symlink_fn=%ps rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, dir->i_op->symlink,
+ READ_ONCE(dir->i_rwsem.owner), current);
int error;
error = may_create_dentry(idmap, dir, dentry);
@@ -5613,6 +5632,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
return error;
error = dir->i_op->symlink(idmap, dir, dentry, oldname);
+ pr_warn("DEBUG VFS: after symlink: dir=%px sb_type=%s error=%d rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, error,
+ READ_ONCE(dir->i_rwsem.owner), current);
if (!error)
fsnotify_create(dir, dentry);
return error;
@@ -5639,6 +5661,10 @@ int filename_symlinkat(struct filename *from, int newdfd, struct filename *to)
if (!error)
error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, from->name, &delegated_inode);
+ pr_warn("DEBUG: after vfs_symlink: error=%d dentry=%px parent=%px parent_inode=%px rwsem owner=%px path_dentry=%px path_inode=%px\n",
+ error, dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(path.dentry)->i_rwsem.count),
+ path.dentry, d_inode(path.dentry));
end_creating_path(&path, dentry);
if (is_delegated(&delegated_inode)) {
error = break_deleg_wait(&delegated_inode);
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 24df4d98f7d2..4c4c6daf8172 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -1629,6 +1629,11 @@ EXPORT_SYMBOL(down_write_trylock);
*/
void up_read(struct rw_semaphore *sem)
{
+ extern void *gfs2_debug_watched_rwsem;
+ if (sem == gfs2_debug_watched_rwsem) {
+ pr_warn("DEBUG WATCHPOINT: up_read on watched rwsem=%px!\n", sem);
+ dump_stack();
+ }
rwsem_release(&sem->dep_map, _RET_IP_);
__up_read(sem);
}
@@ -1639,6 +1644,11 @@ EXPORT_SYMBOL(up_read);
*/
void up_write(struct rw_semaphore *sem)
{
+ extern void *gfs2_debug_watched_rwsem;
+ if (sem == gfs2_debug_watched_rwsem) {
+ pr_warn("DEBUG WATCHPOINT: up_write on watched rwsem=%px!\n", sem);
+ dump_stack();
+ }
rwsem_release(&sem->dep_map, _RET_IP_);
__up_write(sem);
}
--
2.43.0
^ permalink raw reply related [flat|nested] 21+ messages in thread* Forwarded: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
2026-03-05 6:39 [syzbot] [exfat?] [gfs2?] WARNING in filename_symlinkat syzbot
` (8 preceding siblings ...)
2026-03-06 12:38 ` syzbot
@ 2026-03-06 13:12 ` syzbot
9 siblings, 0 replies; 21+ messages in thread
From: syzbot @ 2026-03-06 13:12 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] gfs2: add debug printk to trace existing entry in gfs2_create_inode
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Add a debug printk when gfs2_dir_search finds an existing entry in
gfs2_create_inode. This helps confirm whether the rwsem unlock WARNING
in filename_symlinkat is caused by gfs2_create_inode returning false
success (0) when file is NULL and an existing entry is found on a
corrupted GFS2 image.
The printk logs the directory inode, creation mode, file pointer, found
inode, and rwsem owner at the point where the existing entry is
detected.
This is a temporary diagnostic patch and should be reverted once the
root cause is confirmed.
Reported-by: syzbot+2ed46b6b748df855347f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2ed46b6b748df855347f
Signed-off-by: Deepanshu Kartikey <Kartikey406@gmail.com>
---
fs/gfs2/inode.c | 30 +++++++++++++++++++++++++++++-
fs/namei.c | 30 ++++++++++++++++++++++++++++--
kernel/locking/rwsem.c | 20 ++++++++++++++++++++
3 files changed, 77 insertions(+), 3 deletions(-)
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 8344040ecaf7..2be4a899c665 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -36,6 +36,9 @@
#include "super.h"
#include "glops.h"
+void *gfs2_debug_watched_rwsem;
+EXPORT_SYMBOL(gfs2_debug_watched_rwsem);
+
static const struct inode_operations gfs2_file_iops;
static const struct inode_operations gfs2_dir_iops;
static const struct inode_operations gfs2_symlink_iops;
@@ -725,19 +728,26 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = gfs2_rindex_update(sdp);
if (error)
goto fail;
+ pr_warn("DEBUG GFS2: after glock_nq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
error = gfs2_glock_nq_init(dip->i_gl, LM_ST_EXCLUSIVE, 0, &d_gh);
+ pr_warn("DEBUG GFS2 A: dir=%px rwsem owner=%px\n", dir, READ_ONCE(dir->i_rwsem.owner));
if (error)
goto fail;
gfs2_holder_mark_uninitialized(&gh);
error = create_ok(dip, name, mode);
+ pr_warn("DEBUG GFS2 B: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_gunlock;
inode = gfs2_dir_search(dir, &dentry->d_name, !S_ISREG(mode) || excl);
error = PTR_ERR(inode);
if (!IS_ERR(inode)) {
+ pr_warn("DEBUG GFS2: gfs2_create_inode found existing entry! dir=%px mode=%o file=%px inode=%px S_ISDIR=%d rwsem owner=%px current=%px\n",
+ dir, mode, file, inode, S_ISDIR(inode->i_mode),
+ READ_ONCE(dir->i_rwsem.owner), current);
if (S_ISDIR(inode->i_mode)) {
iput(inode);
inode = NULL;
@@ -759,6 +769,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
}
error = gfs2_diradd_alloc_required(dir, name, &da);
+ pr_warn("DEBUG GFS2 C: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error < 0)
goto fail_gunlock;
@@ -820,16 +831,19 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
blocks++;
error = alloc_dinode(ip, aflags, &blocks);
+ pr_warn("DEBUG GFS2 D: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_free_inode;
gfs2_set_inode_blocks(inode, blocks);
error = gfs2_glock_get(sdp, ip->i_no_addr, &gfs2_inode_glops, CREATE, &ip->i_gl);
+ pr_warn("DEBUG GFS2 D1: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_dealloc_inode;
error = gfs2_glock_get(sdp, ip->i_no_addr, &gfs2_iopen_glops, CREATE, &io_gl);
+ pr_warn("DEBUG GFS2 D2: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_dealloc_inode;
gfs2_cancel_delete_work(io_gl);
@@ -837,13 +851,17 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
retry:
error = insert_inode_locked4(inode, ip->i_no_addr, iget_test, &ip->i_no_addr);
+ pr_warn("DEBUG GFS2 D3: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error == -EBUSY)
goto retry;
if (error)
goto fail_gunlock2;
+ gfs2_debug_watched_rwsem = &dir->i_rwsem;
error = gfs2_glock_nq_init(io_gl, LM_ST_SHARED, GL_EXACT | GL_NOPID,
&ip->i_iopen_gh);
+ gfs2_debug_watched_rwsem = NULL;
+ pr_warn("DEBUG GFS2 E: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_gunlock2;
@@ -862,7 +880,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
}
init_dinode(dip, ip, symname);
gfs2_trans_end(sdp);
-
+ pr_warn("DEBUG GFS2 F: dir=%px rwsem owner=%px\n", dir, READ_ONCE(dir->i_rwsem.owner));
glock_set_object(ip->i_gl, ip);
glock_set_object(io_gl, ip);
gfs2_set_iop(inode);
@@ -888,11 +906,15 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
goto fail_gunlock4;
error = link_dinode(dip, name, ip, &da);
+ pr_warn("DEBUG GFS2 G: dir=%px rwsem owner=%px error=%d\n", dir, READ_ONCE(dir->i_rwsem.owner), error);
if (error)
goto fail_gunlock4;
mark_inode_dirty(inode);
d_instantiate(dentry, inode);
+ pr_warn("DEBUG GFS2 H: dir=%px rwsem owner=%px\n", dir, READ_ONCE(dir->i_rwsem.owner));
+ pr_warn("DEBUG GFS2: before glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
/* After instantiate, errors should result in evict which will destroy
* both inode and iopen glocks properly. */
if (file) {
@@ -900,6 +922,8 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = finish_open(file, dentry, gfs2_open_common);
}
gfs2_glock_dq_uninit(&d_gh);
+ pr_warn("DEBUG GFS2: after glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
gfs2_qa_put(ip);
gfs2_glock_dq_uninit(&gh);
gfs2_glock_put(io_gl);
@@ -937,7 +961,11 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
posix_acl_release(acl);
fail_gunlock:
gfs2_dir_no_add(&da);
+ pr_warn("DEBUG GFS2: fail_gunlock before glock_dq dir=%px rwsem owner=%px current=%px error=%d\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current, error);
gfs2_glock_dq_uninit(&d_gh);
+ pr_warn("DEBUG GFS2: fail_gunlock after glock_dq dir=%px rwsem owner=%px current=%px\n",
+ dir, READ_ONCE(dir->i_rwsem.owner), current);
if (!IS_ERR_OR_NULL(inode)) {
if (inode_state_read_once(inode) & I_NEW)
iget_failed(inode);
diff --git a/fs/namei.c b/fs/namei.c
index 58f715f7657e..768944691e24 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2922,7 +2922,13 @@ static struct dentry *__start_dirop(struct dentry *parent, struct qstr *name,
} else {
inode_lock_nested(dir, I_MUTEX_PARENT);
}
+ pr_warn("DEBUG LOCK: __start_dirop locked dir=%px count=%ld owner=%px current=%px\n",
+ dir, atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
dentry = lookup_one_qstr_excl(name, parent, lookup_flags);
+ pr_warn("DEBUG LOCK: __start_dirop after lookup dir=%px count=%ld owner=%px current=%px dentry_err=%d\n",
+ dir, atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current, IS_ERR(dentry));
if (IS_ERR(dentry))
inode_unlock(dir);
return dentry;
@@ -2944,6 +2950,11 @@ struct dentry *start_dirop(struct dentry *parent, struct qstr *name,
void end_dirop(struct dentry *de)
{
if (!IS_ERR(de)) {
+ struct inode *dir = d_inode(de->d_parent);
+ pr_warn("DEBUG: end_dirop: de=%px parent=%px inode=%px rwsem count=%ld owner=%px current=%px\n",
+ de, de->d_parent, dir,
+ atomic_long_read(&dir->i_rwsem.count),
+ READ_ONCE(dir->i_rwsem.owner), current);
inode_unlock(de->d_parent->d_inode);
dput(de);
}
@@ -4922,7 +4933,9 @@ static struct dentry *filename_create(int dfd, struct filename *name,
dentry = start_dirop(path->dentry, &last, reval_flag | create_flags);
if (IS_ERR(dentry))
goto out_drop_write;
-
+ pr_warn("DEBUG: after start_dirop: dentry=%px parent=%px parent_inode=%px rwsem owner=%px current=%px\n",
+ dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(dentry->d_parent)->i_rwsem.count), current);
if (unlikely(error))
goto fail;
@@ -4959,7 +4972,10 @@ EXPORT_SYMBOL(start_creating_path);
*/
void end_creating_path(const struct path *path, struct dentry *dentry)
{
- end_creating(dentry);
+ if (!IS_ERR(dentry)) {
+ inode_unlock(d_inode(path->dentry));
+ dput(dentry);
+ }
mnt_drop_write(path->mnt);
path_put(path);
}
@@ -5595,6 +5611,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, const char *oldname,
struct delegated_inode *delegated_inode)
{
+ pr_warn("DEBUG VFS: before symlink: dir=%px sb_type=%s symlink_fn=%ps rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, dir->i_op->symlink,
+ READ_ONCE(dir->i_rwsem.owner), current);
int error;
error = may_create_dentry(idmap, dir, dentry);
@@ -5613,6 +5632,9 @@ int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
return error;
error = dir->i_op->symlink(idmap, dir, dentry, oldname);
+ pr_warn("DEBUG VFS: after symlink: dir=%px sb_type=%s error=%d rwsem owner=%px current=%px\n",
+ dir, dir->i_sb->s_type->name, error,
+ READ_ONCE(dir->i_rwsem.owner), current);
if (!error)
fsnotify_create(dir, dentry);
return error;
@@ -5639,6 +5661,10 @@ int filename_symlinkat(struct filename *from, int newdfd, struct filename *to)
if (!error)
error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, from->name, &delegated_inode);
+ pr_warn("DEBUG: after vfs_symlink: error=%d dentry=%px parent=%px parent_inode=%px rwsem owner=%px path_dentry=%px path_inode=%px\n",
+ error, dentry, dentry->d_parent, d_inode(dentry->d_parent),
+ (void *)atomic_long_read(&d_inode(path.dentry)->i_rwsem.count),
+ path.dentry, d_inode(path.dentry));
end_creating_path(&path, dentry);
if (is_delegated(&delegated_inode)) {
error = break_deleg_wait(&delegated_inode);
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 24df4d98f7d2..9c5969a585c6 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -146,6 +146,11 @@ static inline void rwsem_set_owner(struct rw_semaphore *sem)
static inline void rwsem_clear_owner(struct rw_semaphore *sem)
{
+ extern void *gfs2_debug_watched_rwsem;
+ if (sem == gfs2_debug_watched_rwsem) {
+ pr_warn("DEBUG WATCHPOINT: rwsem_clear_owner on watched rwsem=%px!\n", sem);
+ dump_stack();
+ }
lockdep_assert_preemption_disabled();
atomic_long_set(&sem->owner, 0);
}
@@ -1452,6 +1457,11 @@ static inline void __downgrade_write(struct rw_semaphore *sem)
void __init_rwsem(struct rw_semaphore *sem, const char *name,
struct lock_class_key *key)
{
+ extern void *gfs2_debug_watched_rwsem;
+ if (sem == gfs2_debug_watched_rwsem) {
+ pr_warn("DEBUG WATCHPOINT: init_rwsem on watched rwsem=%px!\n", sem);
+ dump_stack();
+ }
init_rwbase_rt(&(sem)->rwbase);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -1629,6 +1639,11 @@ EXPORT_SYMBOL(down_write_trylock);
*/
void up_read(struct rw_semaphore *sem)
{
+ extern void *gfs2_debug_watched_rwsem;
+ if (sem == gfs2_debug_watched_rwsem) {
+ pr_warn("DEBUG WATCHPOINT: up_read on watched rwsem=%px!\n", sem);
+ dump_stack();
+ }
rwsem_release(&sem->dep_map, _RET_IP_);
__up_read(sem);
}
@@ -1639,6 +1654,11 @@ EXPORT_SYMBOL(up_read);
*/
void up_write(struct rw_semaphore *sem)
{
+ extern void *gfs2_debug_watched_rwsem;
+ if (sem == gfs2_debug_watched_rwsem) {
+ pr_warn("DEBUG WATCHPOINT: up_write on watched rwsem=%px!\n", sem);
+ dump_stack();
+ }
rwsem_release(&sem->dep_map, _RET_IP_);
__up_write(sem);
}
--
2.43.0
^ permalink raw reply related [flat|nested] 21+ messages in thread