Hi, This crash occurs due to a mismatched symlink length validation in ext4 when handling corrupted inode data, combined with improper stack expansion handling in GUP. The crash can be reproduced through syzkaller's filesystem stress tests involving symlink operations and direct I/O writes. The key issues are: 1. In __ext4_iget() at fs/ext4/inode.c:5012: inode_set_cached_link() triggers a warning when detecting a symlink with actual length 39 bytes while expecting 29 bytes. This indicates either disk corruption or a kernel bug in symlink length handling. The problem likely stems from improper validation of i_extra_isize and fast symlink storage in ext4_inode. 2. In gup_vma_lookup() at mm/gup.c:1362: The warning "GUP no longer grows the stack" appears when handling VMA lookups for addresses below the stack region. This occurs during direct I/O writes (ext4_dio_write_iter) when pin_user_pages_fast() attempts to access user memory near stack boundaries, but the kernel refuses to expand the stack automatically. Suggested fixes: 1. For ext4: Add stronger validation of i_extra_isize and inline data size before calling inode_set_cached_link() in __ext4_iget 2. For GUP: Re-examine the stack growth policy when handling direct I/O operations near stack boundaries to avoid filesystem corruption cascades This can be reproduced on: HEAD commit: 38fec10eb60d687e30c8c6b5420d86e8149f7557 report: https://pastebin.com/raw/wDUgDsV0 console output : https://pastebin.com/raw/HndaBU1E kernel config : https://pastebin.com/raw/u0Efyj5P C reproducer : part1: https://pastebin.com/raw/3AA1ZHUd part2: https://pastebin.com/raw/0LaFkaAd
