adfs: validate bigdirobnamelen in adfs_fplus_getnext() - #2645
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adfs_fplus_getnext() reads the directory entry name length straight from the on-disk F+ big directory entry: obj->name_len = le32_to_cpu(bde.bigdirobnamelen); ... ret = adfs_dir_copyfrom(obj->name, dir, offset, obj->name_len); obj->name is a fixed size array of ADFS_MAX_NAME_LEN (260) bytes inside the on-stack struct object_info of adfs_fplus_iterate(), but bigdirobnamelen is fully attacker controlled and never validated. Mounting a crafted ADFS image whose big directory entry declares bigdirobnamelen = 264 and then calling getdents64() on the directory makes adfs_dir_copyfrom() write 264 bytes into the 260 byte obj->name, smashing the stack frame of adfs_fplus_iterate(), and the subsequent dir_emit(ctx, obj.name, obj.name_len, ...) reads the same out of bounds range again in filldir64(). adfs_object_fixup() may then append up to four more bytes for the ",xyz" filetype suffix, extending the overflow. Reject entries whose name length exceeds ADFS_FPLUS_NAME_LEN (255). That is the maximum the F+ format can represent, and it also leaves room for the four byte filetype suffix appended by adfs_object_fixup() (255 + 4 = 259 <= ADFS_MAX_NAME_LEN). Reproduced on Linux 7.3.0-rc3 (5dd1818b15d9) with KASAN by mounting a 64 KiB ADFS image (loop, MS_RDONLY) containing a single F+ directory entry with bigdirobnamelen = 264 and calling readdir() on the mount point: ================================================================== BUG: KASAN: stack-out-of-bounds in memchr+0x82/0xb0 Read of size 1 at addr ffff88810099fcac by task init/1 CPU: 3 UID: 0 PID: 1 Comm: init Tainted: G B D 7.3.0-rc3-g5dd1818b15d9 #1 PREEMPT(lazy) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) Call Trace: <TASK> dump_stack_lvl+0x70/0xa0 print_report+0x153/0x4c6 kasan_report+0xf1/0x120 memchr+0x82/0xb0 filldir64+0x56/0x5a0 adfs_fplus_iterate+0x1a6/0x2c0 adfs_iterate+0x1bf/0x4f0 iterate_dir+0x1c1/0x560 __x64_sys_getdents64+0x13a/0x260 do_syscall_64+0xda/0x4b0 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> The buggy address belongs to stack of task init/1 and is located at offset 380 in frame: adfs_fplus_iterate+0x0/0x2c0 This frame has 1 object: [32, 320) 'obj' ================================================================== A matching splat is also produced from adfs_object_fixup+0x3f5/0x480 for the write side of the overflow. With the check in place the same image is rejected with -EIO and no KASAN splat is produced. Fixes: da23ef0 ("adfs: add hexadecimal filetype suffix option") Assisted-by: LLM Signed-off-by: Hui Peng <benquike@gmail.com>
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Superseded by series 1169187 (v1). Closing automatically. Automated by ml2pr |
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Series: https://patchwork.kernel.org/project/linux-fsdevel/list/?series=1169234
Submitter: Hui Peng
Version: 2
Patches: 1/1
Message-ID:
<20260919112521.3872252-1-benquike@gmail.com>Base: vfs.base.ci
Lore: https://lore.kernel.org/linux-fsdevel/20260919112521.3872252-1-benquike@gmail.com
Automated by ml2pr