From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5069729E11D; Mon, 6 Apr 2026 13:49:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775483389; cv=none; b=o1k52yUyQwRaP4IknxYgnpHzPPfz158m/SJZ4VrWVz6E6+di+TC7bqc4I2PTmH5+k93MQcBWD+Ws1sKajy6PB/0KTbpKqUW47XKFvKhOBP8RrcXpHPMqMVCcUMOIsjIvbH7LLYPgyemMbY10Qbcrg7ByEX7MSvAhiTCFZvAOnW4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775483389; c=relaxed/simple; bh=dINbbS4cKF6wwvx/bzeLOYJ+irUgy9XDiVNht/C7qLg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eEKktCXTxD/l0OYQ+9NdAoyGEWPu78aN/bgtr0Ew9ZfvQR3lhjbLsLzgD11AWJFRVbSmlH7kTb4ZUPT7GPNLN5lgbhZn6FC1lcRSxtpkkebjSNOFsDeEUY4CxoWMNNVQ3v0C1xkhwVdFGSYptCERHWjUk7qbkKmjWha/l+qM7tw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Ua2KdIIw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Ua2KdIIw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93C02C4CEF7; Mon, 6 Apr 2026 13:49:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775483388; bh=dINbbS4cKF6wwvx/bzeLOYJ+irUgy9XDiVNht/C7qLg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ua2KdIIwBABAtHiFO3GBaPqNhzbpJxYT5dNJs78uQ4dOKEP9elP9EvXYA1wUQFChT aME3+KnRX2CkmUwexljXI4u8llr/mU6vSY169Tk9O7WgFREyfCXVYMUjoO2h7YlKrE QujcipQUSK0I5HWUEQvyChELsD3UC+WEX16h0HtE= From: Greg Kroah-Hartman To: linux-cifs@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Steve French , Paulo Alcantara , Ronnie Sahlberg , Shyam Prasad N , Tom Talpey , Bharath SM , samba-technical@lists.samba.org, stable Subject: [PATCH 2/2] smb: client: fix OOB reads parsing symlink error response Date: Mon, 6 Apr 2026 15:49:38 +0200 Message-ID: <2026040636-icy-constable-9e17@gregkh> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026040635-banking-unsoiled-3250@gregkh> References: <2026040635-banking-unsoiled-3250@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4719; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=dINbbS4cKF6wwvx/bzeLOYJ+irUgy9XDiVNht/C7qLg=; b=owGbwMvMwCRo6H6F97bub03G02pJDJmXd35I+/nxwhW+O1M5I341Cc1u5Sp4ljd7dxCzxq26h 6fX7xex7YhlYRBkYpAVU2T5so3n6P6KQ4pehranYeawMoEMYeDiFICJ+GkwLNhvPuNZ/EGTyNjf Z5YvPVbPFqHAuZFhvv871jOch70yOfbuaQw6kX4414O7CAA= X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit When a CREATE returns STATUS_STOPPED_ON_SYMLINK, smb2_check_message() returns success without any length validation, leaving the symlink parsers as the only defense against an untrusted server. symlink_data() walks SMB 3.1.1 error contexts with the loop test "p < end", but reads p->ErrorId at offset 4 and p->ErrorDataLength at offset 0. When the server-controlled ErrorDataLength advances p to within 1-7 bytes of end, the next iteration will read past it. When the matching context is found, sym->SymLinkErrorTag is read at offset 4 from p->ErrorContextData with no check that the symlink header itself fits. smb2_parse_symlink_response() then bounds-checks the substitute name using SMB2_SYMLINK_STRUCT_SIZE as the offset of PathBuffer from iov_base. That value is computed as sizeof(smb2_err_rsp) + sizeof(smb2_symlink_err_rsp), which is correct only when ErrorContextCount == 0. With at least one error context the symlink data sits 8 bytes deeper, and each skipped non-matching context shifts it further by 8 + ALIGN(ErrorDataLength, 8). The check is too short, allowing the substitute name read to run past iov_len. The out-of-bound heap bytes are UTF-16-decoded into the symlink target and returned to userspace via readlink(2). Fix this all up by making the loops test require the full context header to fit, rejecting sym if its header runs past end, and bound the substitute name against the actual position of sym->PathBuffer rather than a fixed offset. Because sub_offs and sub_len are 16bits, the pointer math will not overflow here with the new greater-than. Cc: Steve French Cc: Paulo Alcantara Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: linux-cifs@vger.kernel.org Cc: samba-technical@lists.samba.org Cc: stable Assisted-by: gregkh_clanker_t1000 Signed-off-by: Greg Kroah-Hartman --- fs/smb/client/smb2file.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/fs/smb/client/smb2file.c b/fs/smb/client/smb2file.c index ed651c946251..b292aa94a593 100644 --- a/fs/smb/client/smb2file.c +++ b/fs/smb/client/smb2file.c @@ -27,10 +27,11 @@ static struct smb2_symlink_err_rsp *symlink_data(const struct kvec *iov) { struct smb2_err_rsp *err = iov->iov_base; struct smb2_symlink_err_rsp *sym = ERR_PTR(-EINVAL); + u8 *end = (u8 *)err + iov->iov_len; u32 len; if (err->ErrorContextCount) { - struct smb2_error_context_rsp *p, *end; + struct smb2_error_context_rsp *p; len = (u32)err->ErrorContextCount * (offsetof(struct smb2_error_context_rsp, ErrorContextData) + @@ -39,8 +40,7 @@ static struct smb2_symlink_err_rsp *symlink_data(const struct kvec *iov) return ERR_PTR(-EINVAL); p = (struct smb2_error_context_rsp *)err->ErrorData; - end = (struct smb2_error_context_rsp *)((u8 *)err + iov->iov_len); - do { + while ((u8 *)p + sizeof(*p) <= end) { if (le32_to_cpu(p->ErrorId) == SMB2_ERROR_ID_DEFAULT) { sym = (struct smb2_symlink_err_rsp *)p->ErrorContextData; break; @@ -50,14 +50,16 @@ static struct smb2_symlink_err_rsp *symlink_data(const struct kvec *iov) len = ALIGN(le32_to_cpu(p->ErrorDataLength), 8); p = (struct smb2_error_context_rsp *)(p->ErrorContextData + len); - } while (p < end); + } } else if (le32_to_cpu(err->ByteCount) >= sizeof(*sym) && iov->iov_len >= SMB2_SYMLINK_STRUCT_SIZE) { sym = (struct smb2_symlink_err_rsp *)err->ErrorData; } - if (!IS_ERR(sym) && (le32_to_cpu(sym->SymLinkErrorTag) != SYMLINK_ERROR_TAG || - le32_to_cpu(sym->ReparseTag) != IO_REPARSE_TAG_SYMLINK)) + if (!IS_ERR(sym) && + ((u8 *)sym + sizeof(*sym) > end || + le32_to_cpu(sym->SymLinkErrorTag) != SYMLINK_ERROR_TAG || + le32_to_cpu(sym->ReparseTag) != IO_REPARSE_TAG_SYMLINK)) sym = ERR_PTR(-EINVAL); return sym; @@ -128,8 +130,10 @@ int smb2_parse_symlink_response(struct cifs_sb_info *cifs_sb, const struct kvec print_len = le16_to_cpu(sym->PrintNameLength); print_offs = le16_to_cpu(sym->PrintNameOffset); - if (iov->iov_len < SMB2_SYMLINK_STRUCT_SIZE + sub_offs + sub_len || - iov->iov_len < SMB2_SYMLINK_STRUCT_SIZE + print_offs + print_len) + if ((char *)sym->PathBuffer + sub_offs + sub_len > + (char *)iov->iov_base + iov->iov_len || + (char *)sym->PathBuffer + print_offs + print_len > + (char *)iov->iov_base + iov->iov_len) return -EINVAL; return smb2_parse_native_symlink(path, -- 2.53.0