* [PATCH] nsfs: validate file handle type and data in nsfs_fh_to_dentry()
@ 2025-09-21 0:51 Deepanshu Kartikey
0 siblings, 0 replies; 3+ messages in thread
From: Deepanshu Kartikey @ 2025-09-21 0:51 UTC (permalink / raw)
To: syzbot+9eefe09bedd093f156c2
Cc: syzkaller-bugs, linux-ext4, Deepanshu Kartikey
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
Add comprehensive validation of file handle type and data in
nsfs_fh_to_dentry() to prevent processing of handles with incorrect
types or malformed data. This fixes a warning triggered when
open_by_handle_at() is called with invalid handle data on nsfs files.
The issue occurs when a user provides a file handle with an incorrect
handle type or valid FILEID_NSFS type but malformed data structure.
Although the export subsystem routes the call to nsfs, the function
needs to validate that both the handle type and data are appropriate
for nsfs files.
The reproducer sends fh_type=0xf1 (FILEID_NSFS) but with a data
structure from FILEID_INO32_GEN_PARENT, resulting in invalid ns_type
values that trigger warnings in the namespace lookup code.
Reported-by: syzbot+9eefe09bedd093f156c2@syzkaller.appspotmail.com
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
fs/nsfs.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/fs/nsfs.c b/fs/nsfs.c
index 32cb8c835a2b..7f3c8e8c97e2 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -461,8 +461,17 @@ static int nsfs_encode_fh(struct inode *inode, u32 *fh, int *max_len,
static struct dentry *nsfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
int fh_len, int fh_type)
{
+ if (fh_type != FILEID_NSFS)
+ return ERR_PTR(-EINVAL);
+ if (fh_len < sizeof(struct nsfs_file_handle) / sizeof(u32))
+ return ERR_PTR(-EINVAL);
struct path path __free(path_put) = {};
struct nsfs_file_handle *fid = (struct nsfs_file_handle *)fh;
+ if (fid->ns_type != CLONE_NEWNS && fid->ns_type != CLONE_NEWCGROUP &&
+ fid->ns_type != CLONE_NEWUTS && fid->ns_type != CLONE_NEWIPC &&
+ fid->ns_type != CLONE_NEWUSER && fid->ns_type != CLONE_NEWPID &&
+ fid->ns_type != CLONE_NEWNET)
+ return ERR_PTR(-EINVAL);
struct user_namespace *owning_ns = NULL;
struct ns_common *ns;
int ret;
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH] nsfs: validate file handle type and data in nsfs_fh_to_dentry()
@ 2025-09-21 0:53 Deepanshu Kartikey
2025-09-21 2:14 ` [syzbot] [nfs?] WARNING in nsfs_fh_to_dentry syzbot
0 siblings, 1 reply; 3+ messages in thread
From: Deepanshu Kartikey @ 2025-09-21 0:53 UTC (permalink / raw)
To: syzbot+9eefe09bedd093f156c2
Cc: syzkaller-bugs, linux-ext4, Deepanshu Kartikey
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
Add comprehensive validation of file handle type and data in
nsfs_fh_to_dentry() to prevent processing of handles with incorrect
types or malformed data. This fixes a warning triggered when
open_by_handle_at() is called with invalid handle data on nsfs files.
The issue occurs when a user provides a file handle with an incorrect
handle type or valid FILEID_NSFS type but malformed data structure.
Although the export subsystem routes the call to nsfs, the function
needs to validate that both the handle type and data are appropriate
for nsfs files.
The reproducer sends fh_type=0xf1 (FILEID_NSFS) but with a data
structure from FILEID_INO32_GEN_PARENT, resulting in invalid ns_type
values that trigger warnings in the namespace lookup code.
Reported-by: syzbot+9eefe09bedd093f156c2@syzkaller.appspotmail.com
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
fs/nsfs.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/fs/nsfs.c b/fs/nsfs.c
index 32cb8c835a2b..7f3c8e8c97e2 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -461,8 +461,17 @@ static int nsfs_encode_fh(struct inode *inode, u32 *fh, int *max_len,
static struct dentry *nsfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
int fh_len, int fh_type)
{
+ if (fh_type != FILEID_NSFS)
+ return ERR_PTR(-EINVAL);
+ if (fh_len < sizeof(struct nsfs_file_handle) / sizeof(u32))
+ return ERR_PTR(-EINVAL);
struct path path __free(path_put) = {};
struct nsfs_file_handle *fid = (struct nsfs_file_handle *)fh;
+ if (fid->ns_type != CLONE_NEWNS && fid->ns_type != CLONE_NEWCGROUP &&
+ fid->ns_type != CLONE_NEWUTS && fid->ns_type != CLONE_NEWIPC &&
+ fid->ns_type != CLONE_NEWUSER && fid->ns_type != CLONE_NEWPID &&
+ fid->ns_type != CLONE_NEWNET)
+ return ERR_PTR(-EINVAL);
struct user_namespace *owning_ns = NULL;
struct ns_common *ns;
int ret;
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [syzbot] [nfs?] WARNING in nsfs_fh_to_dentry
2025-09-21 0:53 [PATCH] nsfs: validate file handle type and data in nsfs_fh_to_dentry() Deepanshu Kartikey
@ 2025-09-21 2:14 ` syzbot
0 siblings, 0 replies; 3+ messages in thread
From: syzbot @ 2025-09-21 2:14 UTC (permalink / raw)
To: kartikey406, linux-ext4, linux-kernel, syzkaller-bugs
Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in nsfs_fh_to_dentry
------------[ cut here ]------------
WARNING: fs/nsfs.c:502 at nsfs_fh_to_dentry+0xcde/0xe00 fs/nsfs.c:502, CPU#0: syz.0.17/6525
Modules linked in:
CPU: 0 UID: 0 PID: 6525 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:nsfs_fh_to_dentry+0xcde/0xe00 fs/nsfs.c:502
Code: 5c 24 60 e9 08 f8 ff ff e8 2f 01 79 ff 90 0f 0b 90 e9 72 f6 ff ff e8 21 01 79 ff 90 0f 0b 90 e9 da f6 ff ff e8 13 01 79 ff 90 <0f> 0b 90 e9 1a f7 ff ff e8 c5 88 46 09 e8 00 01 79 ff 31 db e9 cd
RSP: 0018:ffffc90003007a20 EFLAGS: 00010293
RAX: ffffffff8247180d RBX: 00000000effffffd RCX: ffff88801bba5ac0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000effffffd
RBP: ffffc90003007b10 R08: ffffffff8fe4db77 R09: 1ffffffff1fc9b6e
R10: dffffc0000000000 R11: fffffbfff1fc9b6f R12: dffffc0000000000
R13: ffff888027365694 R14: ffffffff8e3df738 R15: 0000000000000000
FS: 00007f46068b46c0(0000) GS:ffff8881257a2000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30363fff CR3: 00000000706b4000 CR4: 00000000003526f0
Call Trace:
<TASK>
exportfs_decode_fh_raw+0x178/0x6e0 fs/exportfs/expfs.c:456
do_handle_to_path+0xa4/0x1a0 fs/fhandle.c:276
handle_to_path fs/fhandle.c:400 [inline]
do_handle_open+0x6b4/0x8f0 fs/fhandle.c:415
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f460598ec29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f46068b4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000130
RAX: ffffffffffffffda RBX: 00007f4605bd5fa0 RCX: 00007f460598ec29
RDX: 0000000000400040 RSI: 0000200000000000 RDI: 0000000000000003
RBP: 00007f4605a11e41 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4605bd6038 R14: 00007f4605bd5fa0 R15: 00007ffed9ea2cf8
</TASK>
Tested on:
commit: 846bd222 Add linux-next specific files for 20250919
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10ef70e2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=135377594f35b576
dashboard link: https://syzkaller.appspot.com/bug?extid=9eefe09bedd093f156c2
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch: https://syzkaller.appspot.com/x/patch.diff?x=10e888e2580000
^ permalink raw reply [flat|nested] 3+ messages in thread
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