[PATCH v2 2/2] smb: client: reject a tree connect response whose byte count is too small
Bryam Vargas via B4 Relay <[email protected]>
| Newsgroups | dev.linux.lists.llvm,org.kernel.feeds.b4-sent,org.kernel.vger.linux-cifs,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
From: Bryam Vargas <[email protected]> CIFSTCon() bounds its strnlen() over the byte area with the server's ByteCount minus two, which for ByteCount 0 or 1 goes negative as an int and converts to a huge size_t. The later subtraction wraps the __u16 bytes_left, and that is what bounds cifs_strndup_from_utf16(): a bound of up to 65535 against a ~16 KB cifs_req_poolp object runs off the end of the slab object, and the bytes reach userspace through tcon->nativeFileSystem in /proc/fs/cifs/DebugData. Reject a byte area too small for what the parser consumes. Two bytes is the least the parse can consume, and no conformant response carries fewer -- the Service field is at least "A:" and its NUL. Fixes: cc20c031bb06 ("cifs: convert CIFSTCon to use new unicode helper functions") Cc: [email protected] Signed-off-by: Bryam Vargas <[email protected]> --- fs/smb/client/cifssmb.c | 6 ++++++ fs/smb/client/trace.h | 1 + 2 files changed, 7 insertions(+) diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c index 1f77512252e7..f5aad5f61dce 100644 --- a/fs/smb/client/cifssmb.c +++ b/fs/smb/client/cifssmb.c @@ -615,6 +615,11 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses, tcon->tid = smb_buffer_response->Tid; bcc_ptr = pByteArea(smb_buffer_response); bytes_left = get_bcc(smb_buffer_response); + if (bytes_left < 2) { + rc = smb_EIO2(smb_eio_trace_tcon_bcc_too_small, + bytes_left, 2); + goto out; + } length = strnlen(bcc_ptr, bytes_left - 2); if (smb_buffer->Flags2 & SMBFLG2_UNICODE) is_unicode = true; @@ -670,6 +675,7 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses, reset_cifs_unix_caps(xid, tcon, NULL, NULL); } } +out: cifs_buf_release(smb_buffer); return rc; } diff --git a/fs/smb/client/trace.h b/fs/smb/client/trace.h index 0a91d3aaa079..12241abb8e2e 100644 --- a/fs/smb/client/trace.h +++ b/fs/smb/client/trace.h @@ -133,6 +133,7 @@ EM(smb_eio_trace_sym_slash, "sym_slash") \ EM(smb_eio_trace_sym_target_len, "sym_target_len") \ EM(smb_eio_trace_symlink_file_size, "symlink_file_size") \ + EM(smb_eio_trace_tcon_bcc_too_small, "tcon_bcc_too_small") \ EM(smb_eio_trace_tdis_in_reconnect, "tdis_in_reconnect") \ EM(smb_eio_trace_tx_chained_async, "tx_chained_async") \ EM(smb_eio_trace_tx_compress_failed, "tx_compress_failed") \ -- 2.55.0