From: Tristan Madani Date: Fri, 17 Apr 2026 19:33:17 +0000 (+0000) Subject: ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment X-Git-Tag: v7.0.2~14 X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=922d48fe8c19f388ffa2f709f33acaae4e408de2;p=thirdparty%2Fkernel%2Fstable.git ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment commit 30010c952077a1c89ecdd71fc4d574c75a8f5617 upstream. smb2_get_ea() applies 4-byte alignment padding via memset() after writing each EA entry. The bounds check on buf_free_len is performed before the value memcpy, but the alignment memset fires unconditionally afterward with no check on remaining space. When the EA value exactly fills the remaining buffer (buf_free_len == 0 after value subtraction), the alignment memset writes 1-3 NUL bytes past the buf_free_len boundary. In compound requests where the response buffer is shared across commands, the first command (e.g., READ) can consume most of the buffer, leaving a tight remainder for the QUERY_INFO EA response. The alignment memset then overwrites past the physical kvmalloc allocation into adjacent kernel heap memory. Add a bounds check before the alignment memset to ensure buf_free_len can accommodate the padding bytes. This is the same bug pattern fixed by commit beef2634f81f ("ksmbd: fix potencial OOB in get_file_all_info() for compound requests") and commit fda9522ed6af ("ksmbd: fix OOB write in QUERY_INFO for compound requests"), both of which added bounds checks before unconditional writes in QUERY_INFO response handlers. Cc: stable@vger.kernel.org Fixes: e2b76ab8b5c9 ("ksmbd: add support for read compound") Signed-off-by: Tristan Madani Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index ad8099d5da86..135c74e6c4be 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -4822,6 +4822,8 @@ static int smb2_get_ea(struct ksmbd_work *work, struct ksmbd_file *fp, /* align next xattr entry at 4 byte bundary */ alignment_bytes = ((next_offset + 3) & ~3) - next_offset; if (alignment_bytes) { + if (buf_free_len < alignment_bytes) + break; memset(ptr, '\0', alignment_bytes); ptr += alignment_bytes; next_offset += alignment_bytes;