[PATCH] isofs: Fix handling of directories with tight blocks

[PATCH] isofs: Fix handling of directories with tight blocks

[Jan Kara]

Thomas has reported that after commit b2eb2e288604 ("isofs: Drop support
of directory entries straddling blocks") some isofs images of Fedora
miss some entries in some directories. The problem is triggered when
directory entries are packed in a block in such a way that they exactly
fit the block (which BTW mkisofs doesn't do so I didn't catch this bug
when testing with my images). Fix readdir and lookup code to properly
transition to the next block when directory block is tightly packed.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=2535353
Reported-by: Thomas Schmitt <scdbackup@gmx.net>
Reported-by: Matthias Goergens <matthias.goergens@gmail.com>
Fixes: b2eb2e288604 ("isofs: Drop support of directory entries straddling blocks")
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/isofs/dir.c   | 18 +++++++-----------
 fs/isofs/namei.c | 14 ++++++++------
 2 files changed, 15 insertions(+), 17 deletions(-)

I plan to push this fix to Linus at the end of the week.

diff --git a/fs/isofs/dir.c b/fs/isofs/dir.c
index c7ca7603e97a..5e541e765f54 100644
--- a/fs/isofs/dir.c
+++ b/fs/isofs/dir.c
@@ -110,25 +110,21 @@ static int do_isofs_readdir(struct inode *inode, struct file *file,
 				return 0;
 		}
 
-		de = (struct iso_directory_record *) (bh->b_data + offset);
-
-		de_len = *(unsigned char *)de;
-
+		de = (struct iso_directory_record *)(bh->b_data + offset);
 		/*
-		 * If the length byte is zero, we should move on to the next
-		 * CDROM sector.  If we are at the end of the directory, we
-		 * kick out of the while loop.
+		 * If we are at the end of a block (or at its zero-padded
+		 * tail), move on to the next CDROM sector.  If we are at the
+		 * end of the directory, we'll abort the while loop.
 		 */
-
-		if (de_len == 0) {
+		if (offset >= bufsize || de->length[0] == 0) {
 			brelse(bh);
 			bh = NULL;
-			ctx->pos = (ctx->pos + ISOFS_BLOCK_SIZE) & ~(ISOFS_BLOCK_SIZE - 1);
+			ctx->pos = round_up(ctx->pos, bufsize);
 			block = ctx->pos >> bufbits;
 			offset = 0;
 			continue;
 		}
-
+		de_len = de->length[0];
 		block_saved = block;
 		offset_saved = offset;
 		offset += de_len;
diff --git a/fs/isofs/namei.c b/fs/isofs/namei.c
index 010682f5901a..e7efeea16451 100644
--- a/fs/isofs/namei.c
+++ b/fs/isofs/namei.c
@@ -74,18 +74,20 @@ isofs_find_entry(struct inode *dir, struct dentry *dentry,
 				return 0;
 		}
 
-		de = (struct iso_directory_record *) (bh->b_data + offset);
-
-		de_len = *(unsigned char *) de;
-		if (!de_len) {
+		de = (struct iso_directory_record *)(bh->b_data + offset);
+		/*
+		 * If we are at the end of the block or at its zero-padded
+		 * length, move to the next block.
+		 */
+		if (offset >= bufsize || de->length[0] == 0) {
 			brelse(bh);
 			bh = NULL;
-			f_pos = (f_pos + ISOFS_BLOCK_SIZE) & ~(ISOFS_BLOCK_SIZE - 1);
+			f_pos = round_up(f_pos, bufsize);
 			block = f_pos >> bufbits;
 			offset = 0;
 			continue;
 		}
-
+		de_len = de->length[0];
 		block_saved = bh->b_blocknr;
 		offset_saved = offset;
 		offset += de_len;
-- 
2.51.0

Re: [PATCH] isofs: Fix handling of directories with tight blocks

[Thomas Schmitt]

Hi,

nitpicking about a comment in isofs_find_entry():

> +                * If we are at the end of the block or at its zero-padded
> +                * length, move to the next block.

s/length/tail/

As unprepared reader i would wonder what "zero-padded length" is.
The comment in do_isofs_readdir() says "zero-padded tail", which i
deem more understandable.

As far as the program code is concerned:
Reviewed-by: Thomas Schmitt <scdbackup@gmx.net>


Have a nice day :)

Thomas

Re: [PATCH] isofs: Fix handling of directories with tight blocks

[Jan Kara]

On Tue 22-09-26 16:59:16, Thomas Schmitt wrote:
> Hi,
> 
> nitpicking about a comment in isofs_find_entry():
> 
> > +                * If we are at the end of the block or at its zero-padded
> > +                * length, move to the next block.
> 
> s/length/tail/
> 
> As unprepared reader i would wonder what "zero-padded length" is.
> The comment in do_isofs_readdir() says "zero-padded tail", which i
> deem more understandable.

Good point. Comment fixed.

> As far as the program code is concerned:
> Reviewed-by: Thomas Schmitt <scdbackup@gmx.net>

Thanks!

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

[PATCH] isofs: Always advance to the next block in readdir and lookup

[Matthias Goergens]

Commit 3c01d9263683 ("isofs: Fix handling of directories with tight
blocks") made do_isofs_readdir() and isofs_find_entry() move on to the
next block with pos = round_up(pos, bufsize) both when a record ends
exactly at the end of the block and when the next length byte is zero.
In the second case pos is already block aligned if the zero byte is the
first byte of a block, so round_up() leaves it unchanged, the same block
is read again, and the loop never terminates. There is no
fatal_signal_pending() check in either loop, so the task spins at 100%
CPU and cannot be killed, and a second lookup of the same name blocks in
d_alloc_parallel() and trips the hung task detector.

A block that starts with a zero byte inside a directory is reachable
with a single-byte change to an image made by xorrisofs, and without
any corruption when the logical block size is 512 or 1024 bytes:
ECMA-119 zero-pads a directory only up to the end of the 2048-byte
logical sector, so the later logical blocks of a sector that is less
than full start with zero bytes and lie within the directory's size.

In both walkers pos equals (block << bufbits) + offset, so the next
block is simply block + 1. Advance to it directly, which is right for
both cases.

Fixes: 3c01d9263683 ("isofs: Fix handling of directories with tight blocks")
Signed-off-by: Matthias Goergens <matthias.goergens@gmail.com>
---
Jan, this is on top of your for_next; feel free to fold it into
3c01d9263683 instead if that is easier before you send it to Linus.

 fs/isofs/dir.c   | 4 ++--
 fs/isofs/namei.c | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/isofs/dir.c b/fs/isofs/dir.c
index 5e541e765f547..28741251d56e3 100644
--- a/fs/isofs/dir.c
+++ b/fs/isofs/dir.c
@@ -119,8 +119,8 @@ static int do_isofs_readdir(struct inode *inode, struct file *file,
 		if (offset >= bufsize || de->length[0] == 0) {
 			brelse(bh);
 			bh = NULL;
-			ctx->pos = round_up(ctx->pos, bufsize);
-			block = ctx->pos >> bufbits;
+			block++;
+			ctx->pos = (loff_t)block << bufbits;
 			offset = 0;
 			continue;
 		}
diff --git a/fs/isofs/namei.c b/fs/isofs/namei.c
index e1c571478e8f5..4fba1bf7f0167 100644
--- a/fs/isofs/namei.c
+++ b/fs/isofs/namei.c
@@ -82,8 +82,8 @@ isofs_find_entry(struct inode *dir, struct dentry *dentry,
 		if (offset >= bufsize || de->length[0] == 0) {
 			brelse(bh);
 			bh = NULL;
-			f_pos = round_up(f_pos, bufsize);
-			block = f_pos >> bufbits;
+			block++;
+			f_pos = block << bufbits;
 			offset = 0;
 			continue;
 		}

base-commit: c8437ca3d4386af1ae1f2869643e82fdb9c1f0f5
-- 
2.55.0

Re: [PATCH] isofs: Always advance to the next block in readdir and lookup

[Jan Kara]

On Wed 23-09-26 23:31:34, Matthias Goergens wrote:
> Commit 3c01d9263683 ("isofs: Fix handling of directories with tight
> blocks") made do_isofs_readdir() and isofs_find_entry() move on to the
> next block with pos = round_up(pos, bufsize) both when a record ends
> exactly at the end of the block and when the next length byte is zero.
> In the second case pos is already block aligned if the zero byte is the
> first byte of a block, so round_up() leaves it unchanged, the same block
> is read again, and the loop never terminates. There is no
> fatal_signal_pending() check in either loop, so the task spins at 100%
> CPU and cannot be killed, and a second lookup of the same name blocks in
> d_alloc_parallel() and trips the hung task detector.
> 
> A block that starts with a zero byte inside a directory is reachable
> with a single-byte change to an image made by xorrisofs, and without
> any corruption when the logical block size is 512 or 1024 bytes:
> ECMA-119 zero-pads a directory only up to the end of the 2048-byte
> logical sector, so the later logical blocks of a sector that is less
> than full start with zero bytes and lie within the directory's size.
> 
> In both walkers pos equals (block << bufbits) + offset, so the next
> block is simply block + 1. Advance to it directly, which is right for
> both cases.
> 
> Fixes: 3c01d9263683 ("isofs: Fix handling of directories with tight blocks")
> Signed-off-by: Matthias Goergens <matthias.goergens@gmail.com>
> ---
> Jan, this is on top of your for_next; feel free to fold it into
> 3c01d9263683 instead if that is easier before you send it to Linus.

So I agree what you do is easier to understand so I'll fold it into the
previous commit. Just I'm not sure it is a realistic failure case - that
would mean a directory would contain full block of zeros which I don't
think can happen. Plus this infinite loop was there forever AFAICS and
nobody complained...

								Honza

> 
>  fs/isofs/dir.c   | 4 ++--
>  fs/isofs/namei.c | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/isofs/dir.c b/fs/isofs/dir.c
> index 5e541e765f547..28741251d56e3 100644
> --- a/fs/isofs/dir.c
> +++ b/fs/isofs/dir.c
> @@ -119,8 +119,8 @@ static int do_isofs_readdir(struct inode *inode, struct file *file,
>  		if (offset >= bufsize || de->length[0] == 0) {
>  			brelse(bh);
>  			bh = NULL;
> -			ctx->pos = round_up(ctx->pos, bufsize);
> -			block = ctx->pos >> bufbits;
> +			block++;
> +			ctx->pos = (loff_t)block << bufbits;
>  			offset = 0;
>  			continue;
>  		}
> diff --git a/fs/isofs/namei.c b/fs/isofs/namei.c
> index e1c571478e8f5..4fba1bf7f0167 100644
> --- a/fs/isofs/namei.c
> +++ b/fs/isofs/namei.c
> @@ -82,8 +82,8 @@ isofs_find_entry(struct inode *dir, struct dentry *dentry,
>  		if (offset >= bufsize || de->length[0] == 0) {
>  			brelse(bh);
>  			bh = NULL;
> -			f_pos = round_up(f_pos, bufsize);
> -			block = f_pos >> bufbits;
> +			block++;
> +			f_pos = block << bufbits;
>  			offset = 0;
>  			continue;
>  		}
> 
> base-commit: c8437ca3d4386af1ae1f2869643e82fdb9c1f0f5
> -- 
> 2.55.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] isofs: Always advance to the next block in readdir and lookup

[Matthias Goergens]

On Wed 23-09-26 18:55:11, Jan Kara wrote:
> So I agree what you do is easier to understand so I'll fold it into the
> previous commit. Just I'm not sure it is a realistic failure case - that
> would mean a directory would contain full block of zeros which I don't
> think can happen. Plus this infinite loop was there forever AFAICS and
> nobody complained...

Thanks for folding it in.

Maybe I'm missing something, but I thought the loop came in with
3c01d9263683.  Before it, both walkers advanced with
(pos + ISOFS_BLOCK_SIZE) & ~(ISOFS_BLOCK_SIZE - 1), which moves on even
when pos is already aligned, and mainline lists the reproducer images
fine; only for_next spins on them.  Is there an older path that loops
that I haven't found?

Agreed that a well-formed image with 2048-byte blocks won't have such a
block.  But only the first byte of the directory block has to be zero,
since the walk doesn't look past it: a crafted image needs one byte, and
faulty hardware or an incomplete copy that returns a zeroed sector does
it too.  The task then can't be killed.

Matthias

Re: [PATCH] isofs: Always advance to the next block in readdir and lookup

[Jan Kara]

On Thu 24-09-26 01:52:08, Matthias Goergens wrote:
> On Wed 23-09-26 18:55:11, Jan Kara wrote:
> > So I agree what you do is easier to understand so I'll fold it into the
> > previous commit. Just I'm not sure it is a realistic failure case - that
> > would mean a directory would contain full block of zeros which I don't
> > think can happen. Plus this infinite loop was there forever AFAICS and
> > nobody complained...
> 
> Thanks for folding it in.
> 
> Maybe I'm missing something, but I thought the loop came in with
> 3c01d9263683.  Before it, both walkers advanced with
> (pos + ISOFS_BLOCK_SIZE) & ~(ISOFS_BLOCK_SIZE - 1), which moves on even
> when pos is already aligned, and mainline lists the reproducer images
> fine; only for_next spins on them.  Is there an older path that loops
> that I haven't found?

Hum, right. Today isn't my best day ;) The old code will indeed move to the
next block even if the first byte is 0.

> Agreed that a well-formed image with 2048-byte blocks won't have such a
> block.  But only the first byte of the directory block has to be zero,
> since the walk doesn't look past it: a crafted image needs one byte, and
> faulty hardware or an incomplete copy that returns a zeroed sector does
> it too.  The task then can't be killed.

OK, for corrupted image I agree the looping was possible and it's good to
have that fixed. I just wasn't sure from your explanation whether you don't
have some valid image in mind.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

[syzbot ci] Re: isofs: Fix handling of directories with tight blocks

[syzbot ci]

syzbot ci has tested the following series

[v1] isofs: Fix handling of directories with tight blocks
https://lore.kernel.org/all/20260922121912.2258134-2-jack@suse.cz
* [PATCH] isofs: Fix handling of directories with tight blocks

and found the following issues:
* INFO: task hung in d_alloc_parallel
* INFO: task hung in lookup_slow

Full report is available here:
https://ci.syzbot.org/series/1c5e91af-d857-4245-95ce-5602d6c1fc78

***

INFO: task hung in d_alloc_parallel

tree:      vfs
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/vfs/vfs.git
base:      061b90224ee6e3d51fcfd606d34a1c79365ea1b5
arch:      amd64
compiler:  Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
config:    https://ci.syzbot.org/builds/5fea1b08-98ff-4ff5-8b8d-d7bf6f5a222b/config
syz repro: https://ci.syzbot.org/findings/9651a622-bc22-4db7-91ce-80075a40390b/syz_repro

INFO: task syz.2.19:5860 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.19        state:D stack:28296 pid:5860  tgid:5858  ppid:5737   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5526 [inline]
 __schedule+0x17dd/0x5940 kernel/sched/core.c:7277
 __schedule_loop kernel/sched/core.c:7354 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7369
 d_wait_lookup fs/dcache.c:2775 [inline]
 d_alloc_parallel+0xcdd/0x16b0 fs/dcache.c:2860
 __lookup_slow+0x82/0x2f0 fs/namei.c:1904
 lookup_slow+0x53/0x70 fs/namei.c:1936
 walk_component fs/namei.c:2282 [inline]
 link_path_walk+0xd2a/0x1910 fs/namei.c:2656
 path_lookupat+0xe4/0x8c0 fs/namei.c:2812
 do_o_path+0x9f/0x210 fs/namei.c:4980
 path_openat+0x16c5/0x1da0 fs/namei.c:5002
 do_file_open+0x23e/0x4a0 fs/namei.c:5038
 do_sys_openat2+0x115/0x200 fs/open.c:1442
 do_sys_open fs/open.c:1448 [inline]
 __do_sys_openat fs/open.c:1464 [inline]
 __se_sys_openat fs/open.c:1459 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1459
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2c4d99e159
RSP: 002b:00007f2c4e86b028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f2c4dc26090 RCX: 00007f2c4d99e159
RDX: 0000000000200002 RSI: 0000200000000100 RDI: ffffffffffffff9c
RBP: 00007f2c4da3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2c4dc26128 R14: 00007f2c4dc26090 R15: 00007fffbbb4ebb8
 </TASK>
INFO: task syz.1.18:5866 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.18        state:D stack:28296 pid:5866  tgid:5862  ppid:5736   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5526 [inline]
 __schedule+0x17dd/0x5940 kernel/sched/core.c:7277
 __schedule_loop kernel/sched/core.c:7354 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7369
 d_wait_lookup fs/dcache.c:2775 [inline]
 d_alloc_parallel+0xcdd/0x16b0 fs/dcache.c:2860
 __lookup_slow+0x82/0x2f0 fs/namei.c:1904
 lookup_slow+0x53/0x70 fs/namei.c:1936
 walk_component fs/namei.c:2282 [inline]
 link_path_walk+0xd2a/0x1910 fs/namei.c:2656
 path_lookupat+0xe4/0x8c0 fs/namei.c:2812
 do_o_path+0x9f/0x210 fs/namei.c:4980
 path_openat+0x16c5/0x1da0 fs/namei.c:5002
 do_file_open+0x23e/0x4a0 fs/namei.c:5038
 do_sys_openat2+0x115/0x200 fs/open.c:1442
 do_sys_open fs/open.c:1448 [inline]
 __do_sys_openat fs/open.c:1464 [inline]
 __se_sys_openat fs/open.c:1459 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1459
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f299799e159
RSP: 002b:00007f2996fdd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f2997c26090 RCX: 00007f299799e159
RDX: 0000000000200002 RSI: 0000200000000100 RDI: ffffff
RDX: 0000000000200002 RSI: 0000200000000100 RDI: ffffffffffffff9c
RBP: 00007f2997a3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2997c26128 R14: 00007f2997c26090 R15: 00007ffc5b4deeb8
 </TASK>
INFO: task syz.0.17:5867 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:28296 pid:5867  tgid:5864  ppid:5731   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5526 [inline]
 __schedule+0x17dd/0x5940 kernel/sched/core.c:7277
 __schedule_loop kernel/sched/core.c:7354 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7369
 d_wait_lookup fs/dcache.c:2775 [inline]
 d_alloc_parallel+0xcdd/0x16b0 fs/dcache.c:2860
 __lookup_slow+0x82/0x2f0 fs/namei.c:1904
 lookup_slow+0x53/0x70 fs/namei.c:1936
 walk_component fs/namei.c:2282 [inline]
 link_path_walk+0xd2a/0x1910 fs/namei.c:2656
 path_lookupat+0xe4/0x8c0 fs/namei.c:2812
 do_o_path+0x9f/0x210 fs/namei.c:4980
 path_openat+0x16c5/0x1da0 fs/namei.c:5002
 do_file_open+0x23e/0x4a0 fs/namei.c:5038
 do_sys_openat2+0x115/0x200 fs/open.c:1442
 do_sys_open fs/open.c:1448 [inline]
 __do_sys_openat fs/open.c:1464 [inline]
 __se_sys_openat fs/open.c:1459 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1459
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8d1299e159
RSP: 002b:00007f8d138b4028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f8d12c26090 RCX: 00007f8d1299e159
RDX: 0000000000200002 RSI: 0000200000000100 RDI: ffffffffffffff9c
RBP: 00007f8d12a3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8d12c26128 R14: 00007f8d12c26090 R15: 00007ffda1300988
 </TASK>

Showing all locks held in the system:
locks held by khungtaskd/36: 1, last CPU#1:
 #0: ffffffff8ed5c8e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffffffff8ed5c8e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8ed5c8e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6871
locks held by getty/5424: 2, on CPU#1:
 #0: ffff888172fc30a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc900034832e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360 drivers/tty/n_tty.c:2211
locks held by syz.2.19/5859: 1, last CPU#1:
 #0: ffff88811e2537c0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff88811e2537c0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.2.19/5860: 1, on CPU#1:
 #0: ffff88811e2537c0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff88811e2537c0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.1.18/5863: 2, last CPU#0:
 #0: ffff8881b087b7c0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881b087b7c0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
 #1: ffffffff8eea5ca0 (mmu_notifier_invalidate_range_start){+.+.}-{0:0}, at: fs_reclaim_acquire+0x7c/0x100 mm/page_alloc.c:4392
locks held by syz.1.18/5866: 1, on CPU#1:
 #0: ffff8881b087b7c0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881b087b7c0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.0.17/5865: 1, last CPU#0:
 #0: ffff88811e2532d0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff88811e2532d0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.0.17/5867: 1, on CPU#1:
 #0: ffff88811e2532d0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff88811e2532d0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.3.20/5989: 1, last CPU#1:
 #0: ffff88811e252de0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff88811e252de0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.3.20/5990: 1, on CPU#0:
 #0: ffff88811e252de0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff88811e252de0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.4.21/5992: 1, last CPU#0:
 #0: ffff8881b087b2d0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881b087b2d0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.4.21/5993: 1, on CPU#0:
 #0: ffff8881b087b2d0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881b087b2d0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.5.22/5995: 1, last CPU#0:
 #0: ffff8881b087ade0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881b087ade0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.5.22/5996: 1, on CPU#0:
 #0: ffff8881b087ade0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881b087ade0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.8.25/6124: 1, last CPU#0:
 #0: ffff8881b087a8f0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881b087a8f0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.8.25/6125: 1, on CPU#1:
 #0: ffff8881b087a8f0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881b087a8f0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.7.24/6127: 1, last CPU#1:
 #0: ffff88811e2528f0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff88811e2528f0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.7.24/6130: 1, on CPU#1:
 #0: ffff88811e2528f0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff88811e2528f0 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.6.23/6129: 1, last CPU#0:
 #0: ffff8881b087a400 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881b087a400 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.6.23/6131: 1, on CPU#0:
 #0: ffff8881b087a400 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881b087a400 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.9.26/6247: 2, last CPU#1:
 #0: ffff88811e252400 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff88811e252400 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
 #1: ffffffff8eea5ca0 (mmu_notifier_invalidate_range_start){+.+.}-{0:0}, at: fs_reclaim_acquire+0x7c/0x100 mm/page_alloc.c:4392
locks held by syz.9.26/6248: 1, on CPU#0:
 #0: ffff88811e252400 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff88811e252400 (&type->i_mutex_dir_key#8){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.1.1095/8434: 1, last CPU#1:
 #0: ffffffff8ed5c8e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffffffff8ed5c8e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8ed5c8e0 (rcu_read_lock){....}-{1:3}, at: find_lock_entries+0x12a/0xad0 mm/filemap.c:2188

=============================================

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 36 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:123
 nmi_trigger_cpumask_backtrace+0x17d/0x390 lib/nmi_backtrace.c:66
 trigger_all_cpu_backtrace include/linux/nmi.h:164 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x135/0x170 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xfd7/0x1030 kernel/hung_task.c:561
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 5989 Comm: syz.3.20 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:check_preemption_disabled+0x6/0xd0 lib/smp_processor_id.c:14
Code: c7 c6 60 91 6d 8c eb 1c 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 55 41 57 41 56 53 <65> 8b 05 db 2d af 07 65 48 8b 0d ab 2d af 07 85 c9 74 0c 5b 41 5e
RSP: 0018:ffffc9000273f3a8 EFLAGS: 00000002
RAX: 0000000000000001 RBX: ffffffff8260321f RCX: 0000000000000046
RDX: 0000000000000000 RSI: ffffffff8e4127e6 RDI: ffffffff8c6d9180
RBP: 0000000000000000 R08: ffffc9000273f567 R09: 1ffff920004e7eac
R10: dffffc0000000000 R11: fffff520004e7ead R12: 0000000000000400
R13: 0000000000000800 R14: ffff8881694e8000 R15: 0000000000000022
FS:  00007f30a0bd66c0(0000) GS:ffff8882a8cd0000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b34263fff CR3: 00000001172fe000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 lockdep_hardirqs_off+0x57/0xd0 kernel/locking/lockdep.c:4555
 trace_hardirqs_off+0x12/0x40 kernel/trace/trace_preemptirq.c:104
 lookup_bh_lru fs/buffer.c:1264 [inline]
 find_get_block_common+0x6f/0xe10 fs/buffer.c:1301
 bdev_getblk+0x58/0x6e0 include/linux/gfp.h:-1
 __bread_gfp+0x89/0x380 fs/buffer.c:1412
 sb_bread include/linux/buffer_head.h:383 [inline]
 isofs_bread+0x1d9/0x270 fs/isofs/inode.c:1145
 isofs_find_entry fs/isofs/namei.c:72 [inline]
 isofs_lookup+0x260/0xdc0 fs/isofs/namei.c:162
 __lookup_slow+0x1fb/0x2f0 fs/namei.c:1919
 lookup_slow+0x53/0x70 fs/namei.c:1936
 walk_component fs/namei.c:2282 [inline]
 link_path_walk+0xd2a/0x1910 fs/namei.c:2656
 path_lookupat+0xe4/0x8c0 fs/namei.c:2812
 do_o_path+0x9f/0x210 fs/namei.c:4980
 path_openat+0x16c5/0x1da0 fs/namei.c:5002
 do_file_open+0x23e/0x4a0 fs/namei.c:5038
 do_sys_openat2+0x115/0x200 fs/open.c:1442
 do_sys_open fs/open.c:1448 [inline]
 __do_sys_openat fs/open.c:1464 [inline]
 __se_sys_openat fs/open.c:1459 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1459
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f309fd9e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f30a0bd6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f30a0025fa0 RCX: 00007f309fd9e159
RDX: 0000000000200002 RSI: 00002000000000c0 RDI: ffffffffffffff9c
RBP: 00007f309fe3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f30a0026038 R14: 00007f30a0025fa0 R15: 00007ffdb7dac4f8
 </TASK>


***

INFO: task hung in lookup_slow

tree:      vfs
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/vfs/vfs.git
base:      061b90224ee6e3d51fcfd606d34a1c79365ea1b5
arch:      amd64
compiler:  Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
config:    https://ci.syzbot.org/builds/5fea1b08-98ff-4ff5-8b8d-d7bf6f5a222b/config
syz repro: https://ci.syzbot.org/findings/312b0012-93c1-4dd0-8aaa-a1f18531ccb7/syz_repro

INFO: task syz.1.18:5813 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.18        state:D stack:28704 pid:5813  tgid:5811  ppid:5739
task:syz.1.18        state:D stack:28704 pid:5813  tgid:5811  ppid:5739   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5526 [inline]
 __schedule+0x17dd/0x5940 kernel/sched/core.c:7277
 __schedule_loop kernel/sched/core.c:7354 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7369
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7426
 rwsem_down_read_slowpath+0x6d8/0x980 kernel/locking/rwsem.c:1114
 __down_read_common kernel/locking/rwsem.c:1291 [inline]
 __down_read kernel/locking/rwsem.c:1304 [inline]
 down_read+0x9c/0x330 kernel/locking/rwsem.c:1576
 inode_lock_shared include/linux/fs.h:1039 [inline]
 lookup_slow+0x46/0x70 fs/namei.c:1935
 walk_component fs/namei.c:2282 [inline]
 lookup_last fs/namei.c:2789 [inline]
 path_lookupat+0x3f5/0x8c0 fs/namei.c:2813
 filename_lookup+0x265/0x5d0 fs/namei.c:2842
 user_path_at+0x40/0x160 fs/namei.c:3641
 do_mount fs/namespace.c:4178 [inline]
 __do_sys_mount fs/namespace.c:4395 [inline]
 __se_sys_mount+0x2dc/0x420 fs/namespace.c:4372
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbdcc59e159
RSP: 002b:00007fbdcbbfe028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fbdcc826090 RCX: 00007fbdcc59e159
RDX: 0000000000000000 RSI: 0000200000000240 RDI: 0000000000000000
RBP: 00007fbdcc63506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbdcc826128 R14: 00007fbdcc826090 R15: 00007ffda8e823c8
 </TASK>
INFO: task syz.2.19:5875 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.19        state:D stack:28808 pid:5875  tgid:5870  ppid:5740   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5526 [inline]
 __schedule+0x17dd/0x5940 kernel/sched/core.c:7277
 __schedule_loop kernel/sched/core.c:7354 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7369
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7426
 rwsem_down_read_slowpath+0x6d8/0x980 kernel/locking/rwsem.c:1114
 __down_read_common kernel/locking/rwsem.c:1291 [inline]
 __down_read kernel/locking/rwsem.c:1304 [inline]
 down_read+0x9c/0x330 kernel/locking/rwsem.c:1576
 inode_lock_shared include/linux/fs.h:1039 [inline]
 lookup_slow+0x46/0x70 fs/namei.c:1935
 walk_component fs/namei.c:2282 [inline]
 lookup_last fs/namei.c:2789 [inline]
 path_lookupat+0x3f5/0x8c0 fs/namei.c:2813
 filename_lookup+0x265/0x5d0 fs/namei.c:2842
 user_path_at+0x40/0x160 fs/namei.c:3641
 do_mount fs/namespace.c:4178 [inline]
 __do_sys_mount fs/namespace.c:4395 [inline]
 __se_sys_mount+0x2dc/0x420 fs/namespace.c:4372
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc452d9e159
RSP: 002b:00007fc4523dd028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fc453026090 RCX: 00007fc452d9e159
RDX: 0000000000000000 RSI: 0000200000000240 RDI: 0000000000000000
RBP: 00007fc452e3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc453026128 R14: 00007fc453026090 R15: 00007ffc4eb10368
 </TASK>
INFO: task syz.0.17:5876 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:28808 pid:5876  tgid:5873  ppid:5736   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5526 [inline]
 __schedule+0x17dd/0x5940 kernel/sched/core.c:7277
 __schedule_loop kernel/sched/core.c:7354 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7369
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7426
 rwsem_down_read_slowpath+0x6d8/0x980 kernel/locking/rwsem.c:1114
 __down_read_common kernel/locking/rwsem.c:1291 [inline]
 __down_read kernel/locking/rwsem.c:1304 [inline]
 down_read+0x9c/0x330 kernel/locking/rwsem.c:1576
 inode_lock_shared include/linux/fs.h:1039 [inline]
 lookup_slow+0x46/0x70 fs/namei.c:1935
 walk_component fs/namei.c:2282 [inline]
 lookup_last fs/namei.c:2789 [inline]
 path_lookupat+0x3f5/0x8c0 fs/namei.c:2813
 filename_lookup+0x265/0x5d0 fs/namei.c:2842
 user_path_at+0x40/0x160 fs/namei.c:3641
 do_mount fs/namespace.c:4178 [inline]
 __do_sys_mount fs/namespace.c:4395 [inline]
 __se_sys_mount+0x2dc/0x420 fs/namespace.c:4372
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f615a79e159
RSP: 002b:00007f615b674028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f615aa26090 RCX: 00007f615a79e159
RDX: 0000000000000000 RSI: 0000200000000240 RDI: 0000000000000000
RBP: 00007f615a83506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f615aa26128 R14: 00007f615aa26090 R15: 00007ffc43a846c8
 </TASK>

Showing all locks held in the system:
locks held by khungtaskd/35: 1, last CPU#1:
 #0: ffffffff8ed5c8e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffffffff8ed5c8e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8ed5c8e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6871
locks held by kworker/u10:6/1113: 2, on CPU#1:
 #0: ffff8881000ac140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffff8881000ac140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffff8881000ac140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #0: ffff8881000ac140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
 #1: ffffc90006fb7c40 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #1: ffffc90006fb7c40 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #1: ffffc90006fb7c40 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #1: ffffc90006fb7c40 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
locks held by getty/5423: 2, on CPU#1:
 #0: ffff888175c4b0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc900034762e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360 drivers/tty/n_tty.c:2211
locks held by syz.1.18/5812: 2, last CPU#1:
 #0: ffff8881a249b7c0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
 #0: ffff8881a249b7c0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
 #0: ffff8881a249b7c0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
 #0: ffff8881a249b7c0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:5101
 #1: ffffffff8eea5ca0 (mmu_notifier_invalidate_range_start){+.+.}-{0:0}, at: fs_reclaim_acquire+0x7c/0x100 mm/page_alloc.c:4392
locks held by syz.1.18/5813: 1, on CPU#0:
 #0: ffff8881a249b7c0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881a249b7c0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.2.19/5871: 1, last CPU#0:
 #0: ffff8881a249b2d0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
 #0: ffff8881a249b2d0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
 #0: ffff8881a249b2d0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
 #0: ffff8881a249b2d0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:5101
locks held by syz.2.19/5875: 1, on CPU#1:
 #0: ffff8881a249b2d0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881a249b2d0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.0.17/5874: 1, last CPU#1:
 #0: ffff8881189eb7c0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
 #0: ffff8881189eb7c0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
 #0: ffff8881189eb7c0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
 #0: ffff8881189eb7c0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:5101
locks held by syz.0.17/5876: 1, on CPU#1:
 #0: ffff8881189eb7c0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881189eb7c0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.3.20/5940: 1, last CPU#1:
 #0: ffff8881189eb2d0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
 #0: ffff8881189eb2d0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
 #0: ffff8881189eb2d0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
 #0: ffff8881189eb2d0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:5101
locks held by syz.3.20/5941: 1, on CPU#0:
 #0: ffff8881189eb2d0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881189eb2d0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.5.22/6003: 1, last CPU#0:
 #0: ffff8881a249ade0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
 #0: ffff8881a249ade0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
 #0: ffff8881a249ade0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
 #0: ffff8881a249ade0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:5101
locks held by syz.5.22/6004: 1, on CPU#0:
 #0: ffff8881a249ade0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881a249ade0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.4.21/6006: 1, last CPU#1:
 #0: ffff8881189eade0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
 #0: ffff8881189eade0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
 #0: ffff8881189eade0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
 #0: ffff8881189eade0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:5101
locks held by syz.4.21/6007: 1, on CPU#0:
 #0: ffff8881189eade0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881189eade0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.6.23/6053: 2, last CPU#0:
 #0: ffff8881a249a8f0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
 #0: ffff8881a249a8f0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
 #0: ffff8881a249a8f0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
 #0: ffff8881a249a8f0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:5101
 #1: ffffffff8eea5ca0 (mmu_notifier_invalidate_range_start){+.+.}-{0:0}, at: fs_reclaim_acquire+0x7c/0x100 mm/page_alloc.c:4392
locks held by syz.6.23/6057: 1, on CPU#1:
 #0: ffff8881a249a8f0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881a249a8f0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.7.24/6135: 1, last CPU#0:
 #0: ffff8881a249a400 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
 #0: ffff8881a249a400 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
 #0: ffff8881a249a400 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
 #0: ffff8881a249a400 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:5101
locks held by syz.7.24/6136: 1, on CPU#1:
 #0: ffff8881a249a400 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881a249a400 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.8.25/6138: 1, last CPU#0:
 #0: ffff8881a2499f10 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
 #0: ffff8881a2499f10 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
 #0: ffff8881a2499f10 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
 #0: ffff8881a2499f10 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:5101
locks held by syz.8.25/6139: 1, on CPU#0:
 #0: ffff8881a2499f10 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881a2499f10 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.9.26/6183: 1, last CPU#1:
 #0: ffff8881189ea8f0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
 #0: ffff8881189ea8f0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
 #0: ffff8881189ea8f0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
 #0: ffff8881189ea8f0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:5101
locks held by syz.9.26/6184: 1, on CPU#0:
 #0: ffff8881189ea8f0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline]
 #0: ffff8881189ea8f0 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1935
locks held by syz.1.815/8671: 1, last CPU#0:
 #0: ffff88810ecf03b8 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock include/linux/mmap_lock.h:544 [inline]
 #0: ffff88810ecf03b8 (&mm->mmap_lock){++++}-{4:4}, at: exit_mmap+0x2d8/0x9f0 mm/mmap.c:1323
locks held by syz.2.816/8673: 1, on CPU#1:
 #0: ffffffff8f4f0ed8 (tomoyo_ss){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:198 [inline]
 #0: ffffffff8f4f0ed8 (tomoyo_ss){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:305 [inline]
 #0: ffffffff8f4f0ed8 (tomoyo_ss){.+.+}-{0:0}, at: tomoyo_read_lock security/tomoyo/common.h:1112 [inline]
 #0: ffffffff8f4f0ed8 (tomoyo_ss){.+.+}-{0:0}, at: tomoyo_mount_permission+0x2b5/0x9e0 security/tomoyo/mount.c:238
locks held by modprobe/8675: 1, last CPU#1:
 #0: ffff88817439f678 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock include/linux/mmap_lock.h:544 [inline]
 #0: ffff88817439f678 (&mm->mmap_lock){++++}-{4:4}, at: exit_mmap+0x2d8/0x9f0 mm/mmap.c:1323

=============================================

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 35 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:123
 nmi_trigger_cpumask_backtrace+0x17d/0x390 lib/nmi_backtrace.c:66
 trigger_all_cpu_backtrace include/linux/nmi.h:164 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x135/0x170 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xfd7/0x1030 kernel/hung_task.c:561
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 6138 Comm: syz.8.25 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:__sanitizer_cov_trace_const_cmp8+0x0/0xa0 kernel/kcov.c:316
Code: 74 0a 18 48 89 44 0a 20 c3 cc cc cc cc cc 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <f3> 0f 1e fa 48 8b 04 24 65 48 8b 0d 18 1e cd 11 65 48 8b 15 18 1e
RSP: 0018:ffffc900043df9b8 EFLAGS: 00000246
RAX: f8f8f8f8f8f8f8f8 RBX: ffff8881a2499dd0 RCX: ffff88816b385a00
RDX: 0000000000000000 RSI: 0000000000000022 RDI: 0000000000000000
RBP: ffffc900043dfb30 R08: ffffc900043dfa07 R09: 1ffff9200087bf40
R10: dffffc0000000000 R11: fffff5200087bf41 R12: 1ffff9200087bf38
R13: dffffc0000000000 R14: 0000000000000022 R15: ffffc900043dfa00
FS:  00007f875414d6c0(0000) GS:ffff88818d6d0000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fcd7861f440 CR3: 00000001beb7a000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 isofs_bread+0x15e/0x270 fs/isofs/inode.c:1143
 isofs_find_entry fs/isofs/namei.c:72 [inline]
 isofs_lookup+0x260/0xdc0 fs/isofs/namei.c:162
 lookup_one_qstr_excl+0x12d/0x360 fs/namei.c:1810
 __start_dirop fs/namei.c:2920 [inline]
 start_dirop fs/namei.c:2942 [inline]
 filename_create+0x20e/0x370 fs/namei.c:5101
 filename_mkdirat+0xd2/0x510 fs/namei.c:5445
 __do_sys_mkdirat fs/namei.c:5473 [inline]
 __se_sys_mkdirat+0x35/0x150 fs/namei.c:5470
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f875319e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f875414d028 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007f8753425fa0 RCX: 00007f875319e159
RDX: 00000000000001ff RSI: 0000200000000200 RDI: ffffffffffffff9c
RBP: 00007f875323506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8753426038 R14: 00007f8753425fa0 R15: 00007ffc77a2a958
 </TASK>


***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
  Tested-by: syzbot@syzkaller.appspotmail.com

---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@googlegroups.com.

To test a fix for this bug, please reply with `#syz test`
(on a separate line) and attach the patch to the email.

Notes:
- The patch will be applied on top of the tested series (as an
  incremental fix).
- To test a new version of the whole series, please send it directly
  to syzbot@lists.linux.dev.
- Arguments like custom git repos and branches are not supported.

Re: [PATCH] isofs: Always advance to the next block in readdir and lookup

[Matthias Goergens]

Hi Honza,

On Wed 23-09-26 18:55:11, Jan Kara wrote:
> Just I'm not sure it is a realistic failure case - that
> would mean a directory would contain full block of zeros which I don't
> think can happen.

It does happen on real discs.  About 1% of the disc images I checked
on archive.org have directories that end in a block with no records in
it, mostly from Easy CD Creator 4.0 to 4.2 and Nero.  On for_next
(c8437ca3d438), readdir and lookup in such a directory spin, and stay
stuck after SIGKILL.  This one hangs with default mount options, as the
disc has Rock Ridge and Linux reads its primary tree:

  https://archive.org/details/itsoftcd-39  ITSOFTCD 39.iso
  /PROMOTIONS_SOFTWARE_39/AUTOFLIGHT/DISK13

With my patch on top it lists correctly.  syzbot ci hit the same loop
on your patch, and neither of its reproducers hangs with my patch:

  https://lore.kernel.org/all/6ab5dda9.80e1c6cc.1e8e5f.001f.GAE@google.com/

Thanks,
Matthias