CVE-2026-31614smb: client: fix off-by-8 bounds check in check_wsl_eas()

Official description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix off-by-8 bounds check in check_wsl_eas() The bounds check uses (u8 *)ea + nlen + 1 + vlen as the end of the EA name and value, but ea_data sits at offset sizeof(struct smb2_file_full_ea_info) = 8 from ea, not at offset 0. The strncmp() later reads ea->ea_data[0..nlen-1] and the value bytes follow at ea_data[nlen+1..nlen+vlen], so the actual end is ea->ea_data + nlen + 1 + vlen. Isn't pointer math fun? The earlier check (u8 *)ea > end - sizeof(*ea) only guarantees the 8-byte header is in bounds, but since the last EA is placed within 8 bytes of the end of the response, the name and value bytes are read past the end of iov. Fix this mess all up by using ea->ea_data as the base for the bounds check. An "untrusted" server can use this to leak up to 8 bytes of kernel heap into the EA name comparison and influence which WSL xattr the data is interpreted as.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/bfbc74df8bbe095b3ed68f6d4487b368af087890
• https://git.kernel.org/stable/c/5cc0574c84aa73946ade587c41e81757b8b01cb5
• https://git.kernel.org/stable/c/b2b76d09a64c538c57006180103fc1841e8cfa66
• https://git.kernel.org/stable/c/ba3ad159aa61810bbe0acaf39578b1ebfb6f1a18
• https://git.kernel.org/stable/c/a893f1757d9a4009e4a8d7ceb2312142fe29cea4
• https://git.kernel.org/stable/c/3d8b9d06bd3ac4c6846f5498800b0f5f8062e53b