[syzbot] [isofs?] KASAN: slab-out-of-bounds Read in isofs_fh_to_parent

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a2392f333575 drm/panthor: Clean up FW version information ..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=16de47b0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8cceedf2e27e877d
dashboard link: https://syzkaller.appspot.com/bug?extid=4d7cd7dd0ce1aa8d5c65
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15a1ec3f980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17f623e4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7df8ceab3279/disk-a2392f33.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/42c5af403371/vmlinux-a2392f33.xz
kernel image: https://storage.googleapis.com/syzbot-assets/73599b849e20/Image-a2392f33.gz.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/191f689db82e/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4d7cd7...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 164
==================================================================
BUG: KASAN: slab-out-of-bounds in isofs_fh_to_parent+0x1b8/0x210 fs/isofs/export.c:183
Read of size 4 at addr ffff0000cc030d94 by task syz-executor215/6466

CPU: 1 UID: 0 PID: 6466 Comm: syz-executor215 Not tainted 6.14.0-rc7-syzkaller-ga2392f333575 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call trace:
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:466 (C)
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:408 [inline]
print_report+0x198/0x550 mm/kasan/report.c:521
kasan_report+0xd8/0x138 mm/kasan/report.c:634
__asan_report_load4_noabort+0x20/0x2c mm/kasan/report_generic.c:380
isofs_fh_to_parent+0x1b8/0x210 fs/isofs/export.c:183
exportfs_decode_fh_raw+0x2dc/0x608 fs/exportfs/expfs.c:523
do_handle_to_path+0xa0/0x198 fs/fhandle.c:257
handle_to_path fs/fhandle.c:385 [inline]
do_handle_open+0x8cc/0xb8c fs/fhandle.c:403
__do_sys_open_by_handle_at fs/fhandle.c:443 [inline]
__se_sys_open_by_handle_at fs/fhandle.c:434 [inline]
__arm64_sys_open_by_handle_at+0x80/0x94 fs/fhandle.c:434
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:744
el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:762
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600

Allocated by task 6466:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x40/0x78 mm/kasan/common.c:68
kasan_save_alloc_info+0x40/0x50 mm/kasan/generic.c:562
poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
__kasan_kmalloc+0xac/0xc4 mm/kasan/common.c:394
kasan_kmalloc include/linux/kasan.h:260 [inline]
__do_kmalloc_node mm/slub.c:4294 [inline]
__kmalloc_noprof+0x32c/0x54c mm/slub.c:4306
kmalloc_noprof include/linux/slab.h:905 [inline]
handle_to_path fs/fhandle.c:357 [inline]
do_handle_open+0x5a4/0xb8c fs/fhandle.c:403
__do_sys_open_by_handle_at fs/fhandle.c:443 [inline]
__se_sys_open_by_handle_at fs/fhandle.c:434 [inline]
__arm64_sys_open_by_handle_at+0x80/0x94 fs/fhandle.c:434
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:744
el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:762
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600

The buggy address belongs to the object at ffff0000cc030d80
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes to the right of
allocated 20-byte region [ffff0000cc030d80, ffff0000cc030d94)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10c030
anon flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 05ffc00000000000 ffff0000c0001780 0000000000000000 dead000000000001
raw: 0000000000000000 0000000080400040 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff0000cc030c80: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
ffff0000cc030d00: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
>ffff0000cc030d80: 00 00 04 fc fc fc fc fc fa fb fb fb fc fc fc fc
^
ffff0000cc030e00: 00 00 00 fc fc fc fc fc fa fb fb fb fc fc fc fc
ffff0000cc030e80: 00 00 00 fc fc fc fc fc 00 00 00 fc fc fc fc fc
==================================================================


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

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#syz fix: exact-commit-title

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[Edward Adam Davis]

#syz test

diff --git a/fs/fhandle.c b/fs/fhandle.c
index 3e092ae6d142..a31c0291a473 100644
--- a/fs/fhandle.c
+++ b/fs/fhandle.c
@@ -344,7 +344,7 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
goto out_path;
}
if ((f_handle.handle_bytes > MAX_HANDLE_SZ) ||
- (f_handle.handle_bytes == 0)) {
+ (f_handle.handle_bytes < 16)) {
retval = -EINVAL;
goto out_path;
}

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+4d7cd7...@syzkaller.appspotmail.com
Tested-by: syzbot+4d7cd7...@syzkaller.appspotmail.com

Tested on:

commit: d6b13dbd Merge branch 'for-next/core' into for-kernelci

git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci

console output: https://syzkaller.appspot.com/x/log.txt?x=148de178580000
kernel config: https://syzkaller.appspot.com/x/.config?x=114db1c77c985e53

dashboard link: https://syzkaller.appspot.com/bug?extid=4d7cd7dd0ce1aa8d5c65
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

patch: https://syzkaller.appspot.com/x/patch.diff?x=120a2fb0580000

Note: testing is done by a robot and is best-effort only.

[Edward Adam Davis]

#syz test

diff --git a/fs/isofs/export.c b/fs/isofs/export.c
index 35768a63fb1d..421d247fae52 100644
--- a/fs/isofs/export.c
+++ b/fs/isofs/export.c
@@ -180,7 +180,7 @@ static struct dentry *isofs_fh_to_parent(struct super_block *sb,
return NULL;

return isofs_export_iget(sb,
- fh_len > 2 ? ifid->parent_block : 0,
+ fh_len > 3 ? ifid->parent_block : 0,
ifid->parent_offset,
fh_len > 4 ? ifid->parent_generation : 0);
}

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+4d7cd7...@syzkaller.appspotmail.com
Tested-by: syzbot+4d7cd7...@syzkaller.appspotmail.com

Tested on:

commit: d6b13dbd Merge branch 'for-next/core' into for-kernelci
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci

console output: https://syzkaller.appspot.com/x/log.txt?x=11d92a74580000

kernel config: https://syzkaller.appspot.com/x/.config?x=114db1c77c985e53
dashboard link: https://syzkaller.appspot.com/bug?extid=4d7cd7dd0ce1aa8d5c65
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

patch: https://syzkaller.appspot.com/x/patch.diff?x=1479023f980000

[Edward Adam Davis]

syzbot reported a slab-out-of-bounds Read in isofs_fh_to_parent. [1]

The handle_bytes value passed in by the reproducing program is equal to 12.
In handle_to_path(), only 12 bytes of memory are allocated for the structure
file_handle->f_handle member, which causes an out-of-bounds access when
accessing the member parent_block of the structure isofs_fid in isofs,
because accessing parent_block requires at least 16 bytes of f_handle.
Here, fh_len is used to indirectly confirm that the value of handle_bytes
is greater than 3 before accessing parent_block.

[1]

Reported-by: syzbot+4d7cd7...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=4d7cd7dd0ce1aa8d5c65
Tested-by: syzbot+4d7cd7...@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <ead...@qq.com>
---
fs/isofs/export.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--
2.43.0

[Jan Kara]

Thanks! This is indeed an old bug :). Added to my tree.

Honza

> ---
> fs/isofs/export.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/isofs/export.c b/fs/isofs/export.c
> index 35768a63fb1d..421d247fae52 100644
> --- a/fs/isofs/export.c
> +++ b/fs/isofs/export.c
> @@ -180,7 +180,7 @@ static struct dentry *isofs_fh_to_parent(struct super_block *sb,
> return NULL;
>
> return isofs_export_iget(sb,
> - fh_len > 2 ? ifid->parent_block : 0,
> + fh_len > 3 ? ifid->parent_block : 0,
> ifid->parent_offset,
> fh_len > 4 ? ifid->parent_generation : 0);
> }
> --
> 2.43.0
>

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