From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> mainline inclusion from mainline-v7.1-rc1 commit 3df690bba28edec865cf7190be10708ad0ddd67e category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14418 CVE: CVE-2026-31613 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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: Ronnie Sahlberg <ronniesahlberg@gmail.com> Cc: Shyam Prasad N <sprasad@microsoft.com> Cc: Tom Talpey <tom@talpey.com> Cc: Bharath SM <bharathsm@microsoft.com> Cc: linux-cifs@vger.kernel.org Cc: samba-technical@lists.samba.org Cc: stable <stable@kernel.org> Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.org> Assisted-by: gregkh_clanker_t1000 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Steve French <stfrench@microsoft.com> Conflicts: fs/smb/client/smb2file.c [Commit 215b7f9ecb8d ("smb: client: correctly handle ErrorContextData as a flexible array") change the type of ErrorContextData.] Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com> --- 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 4e7d5c612256..dc91d75aa1bf 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 *)((u8 *)&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; @@ -82,8 +84,10 @@ 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, -- 2.52.0